Auto Uppercase issues!

Mr. Rochester

make a copy of your work then test it there.

always make a copy of your work.

I  am not really sure if the syntax is correct, but you have to unprotect the sheet first before you can make changes, then protect it afterwards.

if you notice, I inserted two lines in your code.

HTH

Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Target.Column > 20 Then Exit Sub
On Error GoTo ErrHandler
Application.EnableEvents = False
ActiveSheet.UnProtect Password:="your password"
Target.Formula = UCase(Target.Formula)
ActiveSheet.Protect Password:="your password"
ErrHandler:
Application.EnableEvents = True
End Sub