How do I make a multi selection on a form in Base?

I have been through as many manuals as I can find and none say the steps to making a multi section in a listbox. It seems straight forward until I actually saved my work and test it, and multi selector still doesn’t work. I’ve gotten it to work a few times but not for long as it always reverts to single selection. What are the trouble shoots?

Leave the listbox empty at design stage and include code similar to as follows:

Dim oDlg As Object

DialogLibraries.LoadLibrary(“Standard”)

oDlg = CreateUnoDialog(DialogLibraries.Standard.MyFormName)

Dim oCtl As Object

oCtl = oDlg.getControl(“ListBox1”)

oCtl.addItem(“Item-x”,0)

oCtl.addItem(“item-y”,1)

oCtl.addItem(“Other”,2)

To find the item selected use code similar to:

Dim sPmt As String

oCtl = oDlg.getControl(“ListBox1”)

sPmt = oCtl.getSelectedItem()