AutoCAD VB :: Copy 3D Polyline Vertically

i am trying to copy 3dpolyline vertically then create another line connecting between the start of each and join all 3 polylines and close them. i got a few hundred of these so programming is key.

can't figure out what's wrong with the code. got all the codes for cloning and create the new 3dpolyline with 2 vertices ok. but just won't join.also tried to going through all the vertices of the new polyline and join. but can't figure out how to read vertices on 3dpolyline.everytime programming something always get stuck at the end. pretty used to it already.

Private Sub btn3dpolybox_Click(sender As System.Object, e As System.EventArgs) Handles btn3dpolybox.Click Me.Hide() 'select 3dpolylines Dim ed As Editor = Application.DocumentManager.MdiActiveDocument.Editor Dim prSelectionOptions As PromptSelectionOptions = New PromptSelectionOptions Dim prSelectionRes As PromptSelectionResult = ed.GetSelection(prSelectionOptions) If prSelectionRes.Status = PromptStatus.Error Then Me.Show() Exit Sub End If If prSelectionRes.Value.Count = 0 Then Else Dim acDoc As Document.
[code]....