Quick newb question

ok so i have this movie, with an empty movie clip inside it called “mcEmpty”, when my movie loads i have the code:

//create an instance of MovieClipLoader
var mcEmpty = new MovieClipLoader();
//load the files into their respective targets

that loads an external .swf and everything works fine. my question is how do i call to an external .swf like the above code, but with a button. i tried fro hours to figure it out and test it but it doesnt want to work. i figure there has to be some changes from 1.0, and im pretty new to this 2.0 coding, so if anyone could help that would be sweet.