Private Sub txtName_Validate(Cancel As Boolean)
  If Trim$(txtName.Text) = "" Then
    MsgBox "Bitte erst Namen eingeben!"
    Cancel = True
  End If
End Sub
 
Private Sub txtMail_Validate(Cancel As Boolean)
  If InStr(txtMail.Text, "@") = 0 Then
    MsgBox "Bitte gültige Mailadresse angeben!"
    Cancel = True
  End If
End Sub