Call function on screen load

I am working on flash application that uses Slideshow screen, now i am trying to call a function when a screen loads; what this function does is it create a focus on one the movie clip.

I tried using the 'onClipEvent(onload) ’ - it does call the function but does not set the focus on it; however if i code setfoucs ( selection.setfoucs) on key handler it sets the focus.

Any help would be appreciated