Need Collapse in accordion mode to take up 100% of parent

[rickthepick]

Hi,
I need the "Collapse" component in accordion mode to always use 100% of its parent. For example, if the parent of "Collapse" is 500 px then the open Panel along with the closed Panels should take up 500 px. Here is an example of a Flash component -- a two panel accordion -- that demonstrates this behavior:

Top Panel: open
Bottom Panel: closed
Accordion Height: 500 px

Top Panel: closed
Bottom Panel: open
Accordion Height: 500 px

Thanks for any help you can give.

[rickthepick]

I can work around this.