Private Sub Worksheet_Change(ByVal Target As Excel.Range)
If Target.Column > 8 Then Exit Sub
On Error GoTo ErrHandler
Application.EnableEvents = False
Target.Formula = UCase(Target.Formula)
ErrHandler:
Application.EnableEvents = True
End Sub
As written, operates on Columns A:H as you enter text in a cell.
Change the 8 to whatever you wish.
This is event code and must go into the sheet module.
Right-click on the sheet tab and "View Code". Copy and paste the above into
that module.