ComboBox: load swf to empty mc

I have an empty movieclip (mc_holder) on the stage into which I want to load any one of three SWFs.

I have a comboBox with three choices, 1,2 and 3, which point to the swf files.

I can do this fairly easily using a button for each swf and behaviours. And by using getUrl I can open the swf in a new browser window. But I can’t figure out how to make the combo box load the swf into the mc_holder.

I thought this was going to be easy …!!

Any ideas?