Holding down mouse slows IE a lot?

[charles_weaver]

I made a simple little example in IE where I draw by holding down the
left mouse button and move the cursor around using a popular Javascript
graphics library to draw and calling drawLine during the MouseMove
event.

In particular I have a line: if (window.event.button != 0)...
drawLine...

If I hold down the button and draw I have to move the mouse fairly
slowly or else it won't keep up. If I remove the if statement and don't
hold the button down it pretty much keeps up all the time. If I hold
the button down while I am drawing, even without the if statement, the
program slows down a lot.

Is this a feature of IE?

Is there a way around this?