Drag object not updating when scrolling source window with SendMessage

[ed0]

Hi,
What I'm trying to do is get the form to scroll when i'm dragging any object near it's border.
I've done this by capturing the mouse position testing if it's near the border and using:

SendMessage(Hold->Handle,WM_VSCROLL,SB_LINEDOWN,0);
SendMessage(Hold->Handle,WM_VSCROLL,SB_ENDSCROLL,0);

This works quite well and scrolls smoothly

My problem arises when the user is dragging something and the form scrolls.
The window repaints properly and the mouse cursor stays in it's proper position
but the object being dragged ends up getting left behind.

So how do I get the handle of the drag object so I can move it?

Thanks for the help,
Ed