<font color=green>' Modul</font>
Option Explicit
Public Db As Database
 
Public Sub OpenDB()
  Set Db = DBEngine.OpenDatabase("Datenbank.mdb")
End Sub

Private Sub cmdSave_Click()
  Dim Rs As Recordset
 
  Set Rs = Db.OpenRecordset("Tabellenname")
  Rs.AddNew
  Rs("Hersteller") = txtHersteller.Text
  Rs("Typ") = txtTyp.Text
  Rs("Seriennummer") = txtSeriennummer.Text
  Rs.Update
  Rs.Close
  Set Rs = Nothing
End Sub

<font color=green>' cmbHersteller füllen</font>
Dim SQL As String
Dim Rs As Recordset
 
SQL = "SELECT Hersteller FROM Tabelle ORDER BY Hersteller"
Set Rs = Db.OpenRecordset(SQL)
If Rs.RecordCount > 0 Then
  With cmbHersteller
    Do Until Rs.Eof
      .AddItem Rs("Hersteller")
      Rs.MoveNext
    Loop
  End With
End If
Rs.Close
Set Rs = Nothing

Private Sub cmbHersteller_Click()
  Dim SQL As String
  Dim Rs As Recordset
 
  With cmbHersteller
    If .ListIndex >= 0 Then
      SQL = "SELECT Typen FROM Tabelle WHERE Hersteller = '" & .Text & "' ORDER" & _
        "By Typen"
      Set Rs = Db.OpenRecordset(SQL)
      If Rs.RecordCount > 0 Then
        Do Until Rs.EOF
          cmbTypen.AddItem Rs("Typ")
          Rs.MoveNext
        Loop
      End If
      Rs.Close
      Set Rs = Nothing
    End If
  End With
End Sub

Private Sub cmbHersteller_Click()
  Dim SQL As String
  Dim Rs As Recordset
 
  With cmbTyp
    If .ListIndex >= 0 Then
      SQL = "SELECT Seriennummer FROM Tabelle WHERE Hersteller = '" & _
        cmbHersteller.Text & "'" & _
      " AND Typ = '" & .Text & "' ORDER By Seriennummer"
      Set Rs = Db.OpenRecordset(SQL)
      If Rs.RecordCount > 0 Then
        Do Until Rs.EOF
          cmbSeriennummer.AddItem Rs("Seriennummer")
          Rs.MoveNext
        Loop
      End If
      Rs.Close
      Set Rs = Nothing
    End If
  End With
End Sub