listbox multiselect

I have a list box B that is polulated from a query of another listbox's A selection. I am trying to make B be multiselect listbox and have the choices made place inanother list box.??

Here is the code i am using

Dim strPara As String

Dim frm As Form, ctl As Control
Dim varItm As Variant

Set frm = Forms!frmMain
Set ctl = frm!lstSubHeading
For Each varItm In ctl.ItemsSelected
Debug.Print ctl.ItemData(varItm)
strPara = "SELECT tblContent.ParaID, tblContent.paraName FROM tblContent INNER JOIN tblSubHeading ON tblContent.SubHeadingID = tblSubHeading.SubHeadingID WHERE tblContent.SubHeadingID = Forms!frmMain!lstSubHeading.ItemData(varItm)"
Me.lstPara.RowSource = strPara
Next varItm



All the items seem to be inorder and are right in the debug windows
but i won't display in the list box

Vishal