Need help with this movie :)

Well when you download and open the fla, you will see 2 seperate shapes with a + and - by their sides. When u press + shape gets bigger and when u press - it gets its original size and return to its starting position.

The thing I couldnt do is:
When I open one of them with + , and I click to the others’ + button I want the first one to be closed and then the 2nd one gets bigger.
I hope you understand.
Many thanks.
Btw this is just a sample Im plannig to put 3-4 more of that shapes.