Flash 8 and the Drawing API

I’m in the process in making a little drawing board using flash Drawing API. Right now i have the lines drawn by using lineTo() but i was wondering if there is a way to erase portions of the line. I know i could just write over it with white but was thinking of a better way. maybe by change the alpha or using a mask something like that. Just wanted to know if anyone came across this before or have a theory that can give me some insight to solve this problem… thanks