Getting swf size for preloader

I am fairly new to actionscripting and would like to try to create a preloader for existing .swf files. Is it at all possible to create a preloader which can determine the size of a seperate .swf file that I would be loading. This would allow me to have a stand-alone preloader for any of my .swf files which would determine total bytes, bytes loaded… I guess what I’m asking is how would I getBytesTotal… for a seperate .swf if possible? Thanks!