Controling movieclips

Hi I’m working on a browser with a flash ui nothing spectacular just a test , anyway I’ve got everything on the programming side working I just want to implement the back forward controls .But I’m having some problems getting everything working .

As you can see from the fla i want the control disabled first then when a mc is loaded ControlType is set to “2” if the user clickes back control type is set to “4”

I have a value called Destination which specifies the mc to add but for some reason it triggers a memory leak or something I can’t understand why can anyone take a look at my movie clip and let me know what I’m doing wrong.