It seems that the proper way to do it is to

• use ClipCursor and to
• get the DX/DY by registering for and handling the WM_INPUT message (http://msdn.microsoft.com/en-us/library/windows/desktop/ms645590(v=vs.85).aspx).

Here's some example of how to use the raw input API:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms645546(v=vs.85).aspx.

EDIT: I also found this interesting post that outlines some possible problems: http://lists.w3.org/Archives/Public/public-webapps/2011JulSep/0847.html

So... anybody got any ideas how to progress with this?

Cas

bumpity bump?

Cas

Found a nice tutorial on the raw input APIs:
http://www.codeproject.com/Articles/17123/Using-Raw-Input-from-C-to-handle-multiple-keyboard

I'm neither a C++ programmer, nor a Win32 programmer nor do I use grabbed cursors. Anyone else up for the job?