treeview item width in custom draw

I asked this some time ago and asking again as I didn't get any response nor could I find the response in any of the existing posts.

Is there a way for me to tell Windows the width of the treeview item I draw myself using custom draw so Windows can setup the horizontal scroll bar based on that width and I'm saved from sub-classing the treeview control's winproc (in order to handle scroll bar notifications and mouse hittesting logic)?

I'm looking for something on the lines of WM_MEASUREITEM that is offered for treeview.

Thanks,

--ANURAG.