33 Chance of 1 of three swf's being loaded? actionscripting required

Hi all, does anyone know how I could incorporate some actionscript to give the user a 33% chance of loading a particular swf file on press of a space bar. I will require three sets of three movie clips on the stage, in which when the user hits the space bar, the user has a 33% chance for each that a particular swf file will load into each of the containers??

Anyone have an idea on how to achieve this???

This does relate to another post i posted but an idea I had on achieving the same desired result.

Thanks for any help, as the time I have on this job is stupid??

Please help