Sub ScratchMacroA()
Dim oRng As Range
Set oRng = ActiveDocument.Range
  With oRng.Find
    .Text = "[0-9]{1,}"
    .MatchWildcards = True
    While .Execute
      If InStr(Left(oRng.Text, 4), "2") > 0 Then
        Select Case Len(oRng.Text)
          Case Is > 4
          Debug.Print Left(oRng.Text, 5)
          Case Is = 4
          Debug.Print oRng.Text
        End Select
      End If
      oRng.End = oRng.Start + 1
    Wend
  End With
lbl_Exit:
  Exit Sub
End Sub
Sub ScratchMacroB()
Dim oRng As Range
Set oRng = ActiveDocument.Range
  With oRng.Find
    .Text = "[0-9]{1,}"
    .MatchWildcards = True
    Do While .Execute
      If InStr(Left(oRng.Text, 4), "2") > 0 Then
        Select Case Len(oRng.Text)
          Case Is > 4
          Debug.Print Left(oRng.Text, 5)
          Exit Do
          Case Is = 4
          Debug.Print oRng.Text
          Exit Do
        End Select
      End If
      oRng.End = oRng.Start + 1
    Loop
  End With
lbl_Exit:
  Exit Sub
End Sub
Sub ScratchMacroC()
Dim oRng As Range
Set oRng = ActiveDocument.Range
Dim lngIndex As Long
  With oRng.Find
    .Text = "[0-9]{1,}"
    .MatchWildcards = True
    While .Execute
      lngIndex = 1
      If InStr(Left(oRng.Text, 4), "2") > 0 Then
        Select Case Len(oRng.Text)
          Case Is > 4
            Debug.Print Left(oRng.Text, 5)
            lngIndex = 5
          Case Is = 4
            Debug.Print oRng.Text
            lngIndex = 4
        End Select
      End If
      oRng.End = oRng.Start + lngIndex
    Wend
  End With
lbl_Exit:
  Exit Sub
End Sub

Sub test1()
Dim oRng As Range
    Set oRng = ActiveDocument.Range
    With oRng.Find
        .text = "aga"
        Do While .Execute
            Debug.Print oRng.text
        Loop
    End With
End Sub

Sub test()
Dim RegEx As Object, Matches As Object, Match As Object
    Set RegEx = CreateObject("VBScript.RegExp")
    With RegEx
        .Global = True
        .Pattern ="(?=\d{0,3}2)\d{4,5}"
    End With
    Set Matches = RegEx.Execute(ActiveDocument.Range.text)
    For Each Match In Matches
        Debug.Print Match.Value
    Next
End Sub

Sub ScratchMacroC()
Dim oRng As Range, oRngProcess As Range
Set oRng = ActiveDocument.Range
Dim lngIndex As Long
  With oRng.Find
    .Text = "[0-9]{1,}"
    .MatchWildcards = True
    While .Execute
      lngIndex = 1
      Set oRngProcess = Nothing
      If InStr(Left(oRng.Text, 4), "2") > 0 Then
        Set oRngProcess = oRng.Duplicate
        Select Case Len(oRng.Text)
          Case Is > 4
            Debug.Print Left(oRng.Text, 5)
            oRngProcess.End = oRngProcess.Start + 5
            lngIndex = 5
          Case Is = 4
            Debug.Print oRng.Text
            oRngProcess.End = oRngProcess.Start + 4
            lngIndex = 4
        End Select
      End If
      oRng.End = oRng.Start + lngIndex
      If Not oRngProcess Is Nothing Then oRngProcess.HighlightColorIndex = wdBrightGreen
    Wend
  End With
lbl_Exit:
  Exit Sub
End Sub

Sub RegExMethod()
Dim RegEx As Object, Matches As Object, Match As Object
Dim oRng As Range
    Set RegEx = CreateObject("VBScript.RegExp")
    With RegEx
        .Global = True
        .Pattern = "(?=(\d){0,3}2)\d{4,5}"
    End With
    Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
    For Each Match In Matches
      Set oRng = ActiveDocument.Range
      With oRng.Find
        .Text = Match.Value
        If .Execute Then
          oRng.HighlightColorIndex = wdYellow
        End If
      End With
    Next
lbl_Exit:
  Exit Sub
End Sub

Sub test()
Dim RegEx As Object, Matches As Object, Match As Object
    Set RegEx = CreateObject("VBScript.RegExp")
    With RegEx
        .Global = True
        .Pattern = "(?=\d{0,3}2)\d{4,5}"
    End With
    Set Matches = RegEx.Execute(ActiveDocument.Range.text)
    For Each Match In Matches
        ActiveDocument.Range(Match.FirstIndex, Match.FirstIndex + Match.Length).HighlightColorIndex = wdBrightGreen
        Debug.Print Match.Value
    Next
End Sub

Sub RegExMethod()
Dim RegEx As Object, Matches As Object, Match As Object
Dim oRng As Range
  Set RegEx = CreateObject("VBScript.RegExp")
  With RegEx
    .Global = True
    .Pattern = "(?=\d{0,3}2)\d{4,5}"
    'Positive lookahead.
    'y = (?=\d{0,3}2) x = \d{4,5}
    'Match second part x only if first part y matches.
    'y matches 2, #2, ##2 or ###2
    'x matches 2####, #2###, ##2##, and ###2# or 2###, #2##, ##2# and ###2
  End With
  Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
  For Each Match In Matches
    ActiveDocument.Range(Match.FirstIndex, Match.FirstIndex + Match.Length).HighlightColorIndex = wdBrightGreen
  Next
lbl_Exit:
  Exit Sub
End Sub

Sub RegEx()
Dim RegEx As Object, Matches As Object, Match As Object
Dim oRng As Range
  Set RegEx = CreateObject("VBScript.RegExp")
  With RegEx
    .Global = True
    .Pattern = "(?=Tom|Jack)\S+ Sprat"
  End With
  Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
  For Each Match In Matches
    'Returns Jack Sprat and Tom Sprat (Not just Sprat like lookback)
    ActiveDocument.Range(Match.FirstIndex, Match.FirstIndex + Match.Length).Select
  Next
lbl_Exit:
  Exit Sub
End Sub

Sub RegEx()
Dim RegEx As Object, Matches As Object, Match As Object
Dim oRng As Range
    Set RegEx = CreateObject("VBScript.RegExp")
    With RegEx
        .Global = True
        .Pattern = "(?=Tom|Jack)\S+ (Sprat)"
    End With
    Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
    For Each Match In Matches
        ActiveDocument.Range(Match.FirstIndex + Match.Length - Len(Match.SubMatches(0)), Match.FirstIndex + Match.Length).HighlightColorIndex = wdBrightGreen
        Debug.Print Match.SubMatches(0)
    Next
lbl_Exit:
  Exit Sub
End Sub

Sub RegExPsuedoLookBack()
Dim RegEx As Object, Matches As Object, Match As Object
Dim oRng As Range
'Sample document text: Jack Sprat, Johnny Sprat, Tom Sprat, Mary Sprat and Bill Sprat.
  'With RegEx look ahead, you can find all instances of x = "Sprat" preceded by either y = "Jack " or y = "Tom "
  Set RegEx = CreateObject("VBScript.RegExp")
  With RegEx
    .Global = True
    .Pattern = "(?=Tom|Jack)\S+ Sprat"
  End With
  Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
  For Each Match In Matches
    'Returns all instances of "Sprat" immediately after "Tom " or "Jack ".
    Debug.Print Match.Value 'Notice the match return includes the proceeding y qualifyer.
  Next
  'A RegEx look back will return all instances of x = "Sprat" preceded by y = "Jack " or y = "Tom " but the match return only inclues the x value "Sprat"
  Set RegEx = CreateObject("VBScript.RegExp")
  With RegEx
    .Global = True
    .Pattern = "(?<=Tom |Jack )\Sprat"
  End With
  On Error GoTo lbl_EH
  Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
  For Each Match In Matches
    'If this worked, it would return all instances of "Sprat" immediately after "Tom " or "Jack ".
    Debug.Print Match.Value
  Next
lbl_ER:
  'VBA workaround for RegEx look back.
  With RegEx
    .Global = True
    'Use a modified look ahead as demonstrated previously.
    .Pattern = "((?=Tom|Jack)\S+ )Sprat" 'Note the addition of parens "()" around the y element will result in a submatch.
  End With
  Set Matches = RegEx.Execute(ActiveDocument.Range.Text)
  For Each Match In Matches
    'Returns x = "Jack Sprat" and "Tom Sprat" matches at before.
    'However, also returns the submatches "Jack " from the "Jack Sprat" match and "Tom " from the "Tom Sprat" match.
    'Use these manipulate the returned range to achieve a VBA pseudo lookback method.
    ActiveDocument.Range(Match.FirstIndex + Len(Match.Submatches(0)), Match.FirstIndex + Match.Length).HighlightColorIndex = wdBrightGreen
  Next
lbl_Exit:
  Exit Sub
lbl_EH:
  MsgBox "Unfortunatley RegEx look back is not supported in VBA." & vbCr + vbCr _
       & "Proceding to work around.", vbInformation + vbOKOnly, "INVALID OPERATION"
  Resume lbl_ER
End Sub

Sub test2()
Dim RegEx As Object, Matches As Object, Match As Object, text As String
    text = "Fellow John John is a good student. Fellow Jack Jack also"
    
    Debug.Print text
    
    Set RegEx = CreateObject("VBScript.RegExp")
    With RegEx
        .Global = True
        .Pattern = "([A-Za-z]+) \1"
        If .test(text) Then
            text = .Replace(text, "$1") ' in every place in string Text where a result is found, that result is replaced with its $1
            
            Debug.Print text
            
        End If
    End With
    
    text = "John Smith is a good student. Jack Sprat also"
    With RegEx
        .Global = True
        .Pattern = "([A-Z][a-z]+) ([A-Z][a-z]+)"
        If .test(text) Then
            text = .Replace(text, "$2 $1")
            
            Debug.Print text
            
        End If
    End With
End Sub