Using SwapDepths in MX?

Hiya guys, I wanted to swap the depths of two movieclips one located in _level0 the other located in _level2! I can get it to work when the MC’s are on the same level but not when thier in different levels.

This is the code I’ve tried…

 _level2.buttons.swapDepths(_level0.caption);

Is there anyway to do this?

Thanks in advance, J