Ciao potresti fare una cosa del genere:
1) Dichiara le 3 costanti
Private Const CHAR_LOWER_A As Integer = 97
Private Const CHAR_LOWER_Z As Integer = 122
Private Const CHAR_STEP As Integer = 32
2) crea la funzione:
Private Function MakeToUpper(KeyAscii As Integer) As Integer
If (KeyAscii >= CHAR_LOWER_A And KeyAscii <= CHAR_LOWER_Z) Then
KeyAscii = KeyAscii - CHAR_STEP
End If
MakeToUpper = KeyAscii
End Function
3) nell' evento OnKeyPress tella textbox scrivi (es:)
Private Sub Text1_KeyPress(KeyAscii As Integer)
KeyAscii = MakeToUpper(KeyAscii)
End Sub
Spero sia quello che cerchi