Sub Example1()
'Burtally slow. Will probably lock up Word.
Dim oPar As Paragraph
Dim lngIndex As Long
Dim lngCount As Long
  For lngIndex = 1 To ActiveDocument.Paragraphs.Count
    Set oPar = ActiveDocument.Paragraphs(lngIndex)
    If InStr(oPar.Range.Text, "XXX") > 0 Then
      lngCount = lngCount + 1
      DoEvents
      'Do something with found text
    End If
  Next
  MsgBox lngCount
lbl_Exit:
  Exit Sub
End Sub

Sub Example2()
'Faster but still slow
Dim oPar As Paragraph
Dim lngCount As Long
  For Each oPar In ActiveDocument.Paragraphs
    If InStr(oPar.Range.Text, "XXX") > 0 Then
      lngCount = lngCount + 1
      DoEvents
      'Do something with found text
    End If
  Next
  MsgBox lngCount
lbl_Exit:
  Exit Sub
End Sub

Sub Example3()
'Even faster
Dim oPar As Paragraph
Dim lngCount As Long
  Set oPar = ActiveDocument.Paragraphs(1)
  Do
    If InStr(oPar.Range.Text, "XXX") > 0 Then
      lngCount = lngCount + 1
      'Do something with found text
    End If
    Set oPar = oPar.Next
  Loop Until oPar.Range.End = ActiveDocument.Range.End
  MsgBox lngCount
End Sub

Sub Example4()
'Likely faster yet because we only look a the paragraphs containing the text to find.
Dim oRng As Range
Dim oPar As Paragraph
Dim lngCount As Long
  Set oRng = ActiveDocument.Range
  With oRng.Find
    .Text = "XXX"
    While .Execute
      lngCount = lngCount + 1
      'Do something with found text
      oRng.Collapse wdCollapseEnd
    Wend
  End With
  MsgBox lngCount
End Sub