Load Second SWF In The First SWF

Ok. I want to load an SWF into a container movie clip and when I click a button I load a new swf into that container. The catch. At the end of the firt SWF I want there to be a preloader that will load the second SWF. I have no idea how to do this so I can use all the help I can get!
Thanks
Fidelity88