Making a unique preloader... I need help

Hi, so I have 3 .swf’s and I want them to run in sequence, where the first one runs for 20 second then plays the next one.

I’m trying to make it so when the first .swf is playing the 2nd .swf is loading in the backround, and then once it’s 100% loaded it drops in front of the previous .swf and plays.

Anyone help?