Determining the end of an external MC

I have a problem.

I have a container_mc that loads in a external MovieClip, lets call it video1.swf using the MovieClipLoader class (it actually contains a video of a 180sx drifting but thats neither here or there). What I’m trying to figure out, is a way to find out when this externally loaded clip terminates, then preload and then display another clip, called video2.swf. I call my preloader and load my external clips into the MCL class using a version I learnt in Senoculars preloader tutorials here http://www.senocular.com/flash/tutorials/preloading/.

Any ideas?