need HELP adding a couple of features to a soundboard I have created for a radio station

I've just created a jingle soundboard to be used by the radio station I work for and I need to add a couple of features to it but the extend of my ability to do what is required has been reached. I'm really hoping someone can give me a few pointers.

Firstly, i need to create a countdown timer that will appear on screen when a jingle button is hit and counts backwards the length of the soundbyte used so that the announcer knows when the jingle is nearing completion. I can create a countdown timer easily enough, but I have no idea how to correlate the length of the soundbyte to the timer. Or do I need to create 72 seperate countdown timers with the known time limit?

Secondly, is there a way of creating a trigger block so that if a button has been hit and is playing a jingle, it is not possible to hit another button until the first jingle has stopped playing?

If anyone could help that would be great, it's just a community station and I'm not being payed for this so any help is great help!

Thanks,