Sub Macro1()
'Graham Mayor - https://www.gmayor.com - Last updated - 01 May 2021 
Dim oPara As Word.Paragraph
Dim oRng As Range
Dim vChar1 As Variant, vChar2 As Variant, vChar3 As Variant
Dim iList As Integer

Const strList1 As String = "A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z"
Const strList2 As String = "a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z"
Const strList3 As String = "0,1,2,3,4,5,6,7,8,9"

    vChar1 = Split(strList1, ",")
    vChar2 = Split(strList2, ",")
    vChar3 = Split(strList3, ",")

    If ActiveDocument.Bookmarks.Exists("Z1") = True Then
        Set oRng = ActiveDocument.Bookmarks("Z1").Range
        For Each oPara In oRng.Paragraphs
            For iList = 0 To UBound(vChar1)
                If oPara.Range.Characters(1) = vChar1(iList) And _
                   oPara.Range.Characters(2) = Chr(46) Then
                    oPara.Style = "Heading 1"
                    GoTo Skip
                End If
            Next iList
            For iList = 0 To UBound(vChar2)
                If oPara.Range.Characters(2) = vChar2(iList) And _
                   oPara.Range.Characters(1) = Chr(40) Then
                    oPara.Style = "Heading 3"
                    GoTo Skip
                End If
            Next iList
            For iList = 0 To UBound(vChar3)
                If oPara.Range.Characters(2) = vChar3(iList) And _
                   oPara.Range.Characters(1) = Chr(40) Then
                    oPara.Style = "Heading 2"
                    GoTo Skip
                End If
            Next iList
Skip:
        Next oPara
    End If
    Set oRng = Nothing
    Set oPara = Nothing
End Sub