You don't actually need a macro for what you've described; it could also be done with a
wildcard Find/Replace, where:
Find = /Ex:*/Ex
Replace = "^&"
and you specify the replacement font colour. A macro equivalent is:
Code:
Sub Demo()
Application.ScreenUpdating = False
With ActiveDocument.Range.Find
.ClearFormatting
.Replacement.ClearFormatting
.Replacement.Font.ColorIndex = wdRed
.Text = "/Ex:*/Ex"
.Replacement.Text = "^&"
.Format = True
.Forward = True
.Wrap = wdFindContinue
.MatchWildcards = True
.Execute Replace:=wdReplaceAll
End With
Application.ScreenUpdating = True
End Sub