Modules & VBA :: Selecting Multiple Values From List In A Form

I am trying to use a list-control on a form to let the user select multiple values. I have understood that this requires some VBA-code to step through the selections in the list, since the "multivalue-selection" is set to "Extended".

When I try to execute the code I have (found and have tried to adjust), then I get the error message "Object required". The "ListCount"-paramater always only results in a ZERO-value, when i step through the code:

Function cmdOpenQuery_Click()
On Error GoTo Err_cmdOpenQuery_Click
Dim MyDB As DAO.Database
Dim qdef As DAO.QueryDef
Dim i As Integer
Dim strSQL As String

[code]....