Well, you just need a series of ifs (or a switch), to change your file when it opens dependant on the value of the resolution.
On the first frame of your file:
ActionScript Code:
if(System.capabilities.screenResolutionX==1024){
//Place your actions for 1024 resolution here
}
else if(System.capabilities.screenResolutionX==800){
//Place your actions for 800 resolution here
}
If you want more flexibility to the values, use a range. That way if someone has a custom resolution, that is dealt with too.
ActionScript Code:
if((System.capabilities.screenResolutionX>1024)&&
(System.capabilities.screenResolutionX<1280)){
//Place your actions here
}
But, with that said...
It is usually better to evaluate the stageSize then the resolution, as that can change based on the browser window. (If someone doesn't have thier browser full screen, but is running @1024, it would still mess up your file.)
To deal with that you would also have to set your Stage scale to false.