how to write a recursive function to create a treeview from data in datawindow?

I have a parent-child data in a datawindow from a table mytab(id, pid....)

Then I want to use to data to create a tree in treeview.

I try to use recursive function, but have problem with datawindow as I use filter to change the data in datawindow.

here is my code:

    of_addnode(treeviewitem node, rootrow):

    int li_rows,li_newitem, i

    treeviewitem li_tvitem

    dw_1.SetFilter("pid = " + string(node.data))

    dw_1.Filter( )

    li_rows =  dw_1.RowCount()

    if li_rows = 0 then

    return

    end if

    for i = 1 to li_rows

    li_tvitem.level = node.level +1

    li_tvitem.data = dw_1.GetItemNumber(i,"id")

    li_tvitem.label = dw_1.GetItemString(i,"description")

    li_tvitem.pictureindex = 1

    li_tvitem.selectedpictureindex = 2

    li_newitem = tv_1.insertitemsort (rootrow, li_tvitem)  // insert a new node

    of_addnode(li_tvitem,li_newitem)

    dw_1.SetFilter("pid = " + string(node.data))  //restore data back to filter, problem here. tree will have duplicate item

            dw_1.Filter( )

    next

how to create a recursive function from one datasource datawindow for this case?