Dim rsOld As New ADODB.RecordSet
    Dim rsNew As New ADODB.RecordSet
    Dim fld As ADODB.field
    Dim sql As String
 
    ' Create and open a new Recordset
    'Set rsOld = New ADODB.RecordSet
    sql = "Select * from [Service/Reparaturen] where lnr = " & tbServiceNr.Text
    openTable rsOld, sql
    'Debug.Print rsOld.recordCount
 
    'Set rsNew = New ADODB.RecordSet
    sql = "Select * from [Service/Reparaturen] where lnr = " & tbServiceNr.Text
    openTable rsNew, sql
    Debug.Print rsNew.recordCount
 
    If Not rsOld.EOF Then
        rsNew.AddNew
            For Each fld In rsOld.Fields
                If fld.Name <> "lnr" Then rsNew(fld.Name) = fld.Value
            Next
            rsNew!stammdatum = True
        rsNew.Update
    End If

Gruss Michael