Private Sub CBNachname_LostFocus() 
If InStr(0, CBNachname.Text, "0") Or InStr(0, CBNachname.Text, "1") Or InStr(0, _
  CBNachname.Text, "2") Or _
    InStr(0, CBNachname.Text, "3") Or InStr(0, CBNachname.Text, "4") Or InStr( _
    0, CBNachname.Text, "5") Or _
    InStr(0, CBNachname.Text, "6") Or InStr(0, CBNachname.Text, "7") Or InStr( _
    0, CBNachname.Text, "8") Or _
    InStr(0, CBNachname.Text, "9") Then
    MsgBox "Es sind Zahlen enthalten"
Else
MsgBox "keine Zahlen"
End If
 
     End Sub

Nichts ist umsonst!