Drag and Drop video sequence

I have a project that is going to require some drag and drop scripts. That part I can figure out, but thats not the hard part. I am going to have 6 movies that will be able to be put in a sequence in any order the user wants, again, this part is not hard.

Where it gets tricky is we need to be able to basically hit a play button that only works once all the clips are in the sequence area, then have the videos play in the order that they are currently in, no matter what the sequence is. The user has to be able to put the videos in any order, and have the sequence of video’s play in that order, there is where i get lost. I haven’t starting writing this yet as I want to see if it’s something i can find enough info about first to even try.

I am somewhat versed in actionscript, but would still consider myself a beginner. Again, I can get the drag and drop movements, I will need help making the play button only active when all the clips are in the sequence, and making the movies (which will probably be movieClips) play in the given order that are in. Any ideas? Thanks ahead of time for all the help.