Even the macro recorder would give you a useable macro if you plugged the Find/Replace into it. That said, try:
Code:
Sub Demo()
Application.ScreenUpdating = False
With ActiveDocument.Range
With .Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = "([0-9])^13"
.Replacement.Text = "\1^t"
.Forward = True
.Format = False
.Wrap = wdFindContinue
.MatchWildcards = True
.Execute Replace:=wdReplaceAll
End With
End With
Application.ScreenUpdating = True
End Sub
For PC macro installation & usage instructions, see:
Installing Macros
For Mac macro installation & usage instructions, see:
Word:mac - Install a Macro