Private Sub NewTech_Click() 'Neue Technology in Tabelle einfügen
On Error GoTo Err_NewTech_Click
    Dim Vorhanden As Integer
    'Prüfung: 1.Feld nicht leer? 2.TechName noch nicht vorhanden?
    If Not IsNull(NewTechField) Then
            MsgBox "erster If Zweig 1", vbOKOnly
            Vorhanden = XDLookup(" & NewTechField.Value & ", "Technology")
            MsgBox "erster If Zweig 2", vbOKOnly
            If Not IsNull(Vorhanden) Then
                MsgBox "Please choose a New Name", vbCritical
            Else
                MsgBox "Insert Zweig", vbOKOnly
                DB.Execute "INSERT INTO TECHNOLOGY (TechName) VALUES ('" & _
                  NewTechField.Value & "')"
                MsgBox "New Data was added...", vbOKOnly
            End If
    Else
        MsgBox "Please fill out: New Technology", vbCritical
    End If
Exit_NewTech_Click:
    Exit Sub
Err_NewTech_Click:
    MsgBox Err.Description
    Resume Exit_NewTech_Click
End Sub

Vorhanden = XDLookup(" & NewTechField.Value & ", "Technology")

 If Not IsNull(NewTechField) Then

blutiger Anf?nger...