I'm writing a license agreement dialog box with Win32 and I'm stumped. As usual with these things I want the "accept/don't accept" buttons to become enabled when the slider of the scroll bar of the richedit control hits bottom, but I can't find a way to get notified of that event. The earliest I've been able to learn about it is when the user releases the left mouse button.

Is there a way to do this?

Here's what I tried so far: 

* `WM_VSCROLL` and `WM_LBUTTONUP` in richedit's wndproc
* `EN_MSGFILTER` notification in dlgproc (yes the filter mask is getting set)
* `WM_VSCROLL` and `WM_LBUTTONUP` in dlgproc.
* `EN_VSCROLL` notification in dlgproc

I got so desperate I tried polling but that didn't work either because apparently timer messages stop arriving while the mouse button is down on the slider. I tried both:

* timer callback (to poll) in dlgproc
* timer callback (to poll) in richedit's wndproc