API-draw: check if line intersects another line

It been a while and I need some help on this one…

I’m making a very simple game that lets you draw a curve by hand (using lineTo to the mouse position on mousemove) but now, I need to check wether the line intersects wiith another part of the same line (e.g. a loop)

I first used an onrollover command, and that worked, but not always because the mouse moved too fast (same with hittest with mouse). Then I pre-drawed the line in another mc, used hittest on it, and if it wasn’t intersecting, draw it in the real mc. But that didn’t work because it used the bounds to test. I guess the best way is to use some mathematical formula, but that would mean I have to save all my coordinates in an array…

Is there another way?

TIA