Problem with Draw Lines

Hi

I am creating multiline charts in flash using data from XML file.
You can see record of one student at a time. You have next button to go for the next students chart data. I am able to generate the lines for next record also. But my previous students lines are also their, its not getting deleted/cleared. I have tried with …movieclip.clear() also…but couldnt get through.

Can anyone help me out with this…

Thanx
Ash