Need help inserting actionscript in a .swf file

i used a third-party software (Screenflash) to create a .swf file that’s basically just a movie clip showing recorded screen captures. it doesn’t generate any source .fla file.

i’ve successfully created a “loader” program using flash mx that loads this .swf file with the loadMovie command.

my problem is that i need to insert a stop(); action at the start of the .swf file so that it won’t play outside of my “loader” program.

i’ve tried creating a .fla file that contains only the .swf movieclip (created by Screenflash) so i can add my actionscript on another layer; but upon testing or exporting, the .swf movieclip displays at a size/proportion much bigger than the original.

any advise will be greatly appreciated!