Locking frameset Vertical Scroll bar


In my current site. I am using frameset. Tol section is for header left section for body content and right side frame is for shopping card section.

When Body section content grows the vertical scroll bar appears. Here is the scenario for solution I need;

In side body section frame I have a link. By clicking that link an overlay window opens. but still I can able to scroll the mail section of the frame.

When pop up opens I want to lock the vertical scroll bar to moving up or down. and when I close the pop up window then again the scroll bar will get activate.

I have attached the screenshot Please check and give me some solution for it.

Thanks in Advance