Yes, mousemovex() and mousemovey()
Unless thats only DBP, in which case you could still make a function to get the speed based on subtracting the old mouse positions from the new to get the difference.
<EDIT>
Which it looks to be what you've done, the only change I'd make is not to give the absolute of the speed, having negative values is much more useful (so when the value is negative the mouse is moving to the left, and opposite for when its positive, allowing you to turn objects properly). After you've gotten the speed, just multiplty it by some sensitivity and use those two values to rotate the camera/object/whatever.