GtkTreeView : Create a child row with different model than it's parent row?

[Paul Stuart <Paul_Stuart seektech com>]

Hi,
   I have a treeview interface with five or so columns of  "stuff" (text) that spans the screen -easy- but I'd like to have the child of that row be a single progress bar that also spans the length of the screen. 

If I just create a column for the progress bar, when the row is expanded, the columns of the parent are pushed out of the window to make room for the progress bar.

 I'd really like for all the parent columns to stay fixed in place and show the progress bar below them. Is there any way to accomplish this? It sounds like I need one treeview model for the parent row with a different model for the child nested within it. 

Hopefully what I'm trying to say is clear, very new to the GtkTreeview.

Any ideas?

Thanks,
Paul