Audio off & on

I have a lingering question that I cannot seem to get past.
I have a project which I have to do that needs to have a sound Off/On button.
I assume that in order to do this you have got to build an interface frame with the off/on button. Then I am loading my .swf into the interface by targeting a blank MC.
It works fine with the first swf that I load I can shut off or turn on the sound with no problem.
The problem begins when I unload the first movie then load the second movie in the same place. the sound button no longer works.

Any ideas or help someone might offer would be greatly appreciated.