packing in cellrenderers

[B McAndrews <bmcandrews efs-us com>]

I've been able to pack multiple cell renderers into a TreeView column, 
but it appears that the packing is done across the width of the cell. 
Is it possible to have the cells packed "on-top" of each other, ie:

____________
| first   second |
| third  fourth  |
-------------------

where first,second, ... each have their own cellrenderer?  I think that 
I can put newlines into a cellrederertext to get the same result 
("first\nsecond"), yet I'd like to be able to tie each of the
values to something in the model.

Thanks

--
Brian