Well, here comes your graphics-trouble-maker:

I got PictureBox and I have drawn a curve on it.

Now using my mouse I draw a vertical line on the curve.

The problem is that (as you may have already guessed) I have to erase the PREVIOUS vertical line before I draw the NEW vertical line so that I can have line-following-mouse effect. To delete the previous line I draw it in the background (gray) color, yes now I have deleted the line and I can draw my new line but o-oh there's bad effect that I can't prevent, since the old vertical line intersects the curve at one point and I re-draw it using the background color I also delete one point of my lovely curve and repeating this effect all the time I can see my curve disappeat slowly.

How can I have that vertical-line-drawn-over-the-static-curve-and-following-mouse-without-disturbing-the-previously-drawn-static-curve effect?

I think I'm missing some point.

Please give me a detailed example (that means telling me much more than "use that DrawMode = vbXorPen" ).

Thanks in advance...