You can't choose a default uppercase format, but you can run an event
macro that changes text to uppercase:
Put this in the Worksheet code module (right-click on the worksheet tab
and choose view code):
Private Sub Worksheet_Change(ByVal Target As Excel.Range)
With Target
If .Count = 1 Then
If .Column = 1 Then
If Not (IsEmpty(.Value) Or _
IsNumeric(.Value) Or .HasFormula) Then
Application.EnableEvents = False
.Value = UCase(.Value)
Application.EnableEvents = True
End If
End If
End If
End With
End Sub