Private Sub txt1_LostFocus()
Dim i As Integer
Dim s As String
For i = 1 To Len(txt1.Text)
s = Mid(txt1.Text, i, 1)
If (s < "0" Or s > "9") And (s < "a" Or s > "z") Then
MsgBox "???C C? C?ICI C?E?CI? ??C??I", vbCritical + vbMsgBoxRight, "I?C"
txt1.Text = ""
txt1.SetFocus
Exit For
End If
Next i
End Sub