How can I preselect Items in a ListBox on a form to display as Selected when the Form Loads

The Following does NOT work

nCount = THISFORM.LstID.ListCount
FOR n = 1 TO nCount
THISFORM.LstID.Selected(n) = .T.
NEXT

Note : THISFORM.LstID.RowSourceType = 2 Alias
and THISFORM.LstID.MultiSelect = .T.