Loading swf in sequence

I have a main movie with 12 buttons (numbered 1-12), each button loads the relevant swf into a blank ‘content’ MC on the main stage.

I also need to have 1 button called ‘start’ which plays whichever swf is due next. ie; if you are on swf no. 3 pressing start will load swf no. 4.

How do I do this, what do I need to look into?

I guess a simple way would be to have the ‘start’ button tell the ‘content’ movie to go to a certain frame which has an action on it to load whichever movie is next… ???

thanks for any help