I was unable to make that work: but this version seems to fit the bill.
Code:
Dim lngRow As Long
For lngRow = 0 To Me!lstAttendees.ListCount - 1
If Me.lstAttendees.ItemData(lngRow) = pubSchAssociate Then
Me!lstAttendees.Selected(lngRow) = True
End If
Next
Where pubSchAssociate is a public variable with the Primary Key stored from a previous operation.