Public Function CDateSQL(vardatum As Variant) As String
    If IsDate(vardatum) Then
        CDateSQL = Format(CDate(vardatum), "'yyyy-mm-dd'")
    End If
End Function

Public Function aDoLookupSQL(ByVal sSQL As String, Optional conAlternativ As ADODB.Connection = Null) As Variant

    Dim rst As ADODB.Recordset
    Dim con As ADODB.Connection
    
    If conAlternativ Is Nothing Then
        Set con = CurrentProject.Connection
    Else
        Set con = conAlternativ
    End If

On Error GoTo HandleErr

    Set rst = New ADODB.Recordset
    With rst
        .Open sSQL, con, adOpenForwardOnly, adLockReadOnly
        If .BOF Then
            aDoLookupSQL = Null
        Else
            aDoLookupSQL = .Fields(0)
        End If
        .Close
    End With
    
ExitHere:
    Set rst = Nothing
    Exit Function

HandleErr:
    aDoLookupSQL = Null
    Resume ExitHere

End Function

Public Function aDoLookup(feld As String, tabelle As String, where As String) As Variant
    Dim strSQL As String
    strSQL = "SELECT " & feld & " FROM " & tabelle & " WHERE " & where
    aDoLookup = aDoLookupSQL(strSQL)
End Function