Need some help with GUI design: 2 header rows in a treeview

[Daniel Kasak <dkasak nusconsulting com au>]

Hi all.

I'm working on a data entry form that would *really* benefit from having 
2 rows of headers for the treeview.

I've done this sort of thing before with treeviews where all the columns 
fit in the treeview without scrolling, by having an hbox filled with 
buttons immediately above the treeview, and then just resizing the 
buttons when the treeview is resized so the buttons line up with the 
columns they're supposed to go above. This actually doesn't look too 
hacked up :)

I've tried to reproduce this method with my current treeview, which 
scrolls way out to the right, but I've hit a problem. I can't actually 
put the hbox pull of buttons inside the scrolled window, because if I 
do, the scrolled window ceases to operate as a scrolled window - the 
treeview isn't scrollable. I assume you can't do this. What, then, do I do?

Here is a screenshot of what I've got so far:
http://www.nusconsulting.com.au/internal/energy_datasheet.jpg

The 'Invoice' button should extend across the 1st 2 columns, the Energy 
kWh button should cover the red columns, the Network kWh button should 
be only partly visible, and the other buttons should be invisible ... 
until the treeview is scrolled across to the right, and then they also 
scroll across. Is this possible? Or maybe I can hide the default 
treeview header and replace it with my own stuff packed in a table or 
something?

--
Daniel Kasak
IT Developer
NUS Consulting Group
Level 5, 77 Pacific Highway
North Sydney, NSW, Australia 2060
T: (+61) 2 9922-7676 / F: (+61) 2 9922 7989
email: dkasak nusconsulting com au
website: http://www.nusconsulting.com.au