Why is 'setvaluator' such a dog?

[Tim Hall]

I want to create some sliders that give offsets.  The way I was
doing this was to reset the cursor position, using 'setvaluator',
after each MOUSEX event.  However this makes a previously smooth
motion (controlled by the slider) become jumpy. I narrowed down
the problem to the setvaluator call.  Sooo...

1) Why is 'setvaluator' so slow?

2) Is there another faster way to reposition the cursor or freeze
	the cursor while still getting MOUSE events?

-Tim
tjh at bu-pub.bu.edu