Why does this -> ActiveDocument.FormFields.count equal zero?

Hi all, I've added numerous listboxes to my document using the "Control Toolbox" Toolbar. Now when I use the following VBA:
Dim aDoc As Word.Document
Set aDoc = ActiveDocument
MsgBox (aDoc.FormFields.Count)

I get a message box that says "0".

The reason I'm doing this is that I would like iterate over all the listboxes in the document.

Thanks,
Novice