You're welcome. If I may add the lboHosCat_AfterUpdate sub could even be rewritten as this:
Private Sub lboHosCat_AfterUpdate()
Dim qdf As QueryDef
Set qdf = CurrentDb.QueryDefs(IIf(Me!lboHosCat.Selected(Me!lboHosCat.ListIndex),"qryAppCatID","qryRemCatID"))...