Assuming the CF is intended for all cells in col. "A" - I would suggest an
Event-Macro:
-------------------------------------------------------------------------------
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 1 Then
For C = 1 To Len(Target)
If Asc(Mid(Target, C, 1)) > 64 And Asc(Mid(Target, C, 1)) < 91 Then
Target.Characters(Start:=C, Length:=1).Font.ColorIndex = 3
End If
Next
End If
End Sub