Audio Clip Syncronisation Help!

I am making a music app for my final year project. Games Design btw.

It allows the user to create their own backing tracks by selecting loops to play and there are many loops for different instruments.

Each instrument type is assigned to its own Audio-source to allow multiple clips playing at once but to also prevent clips of the same instrument playing at the same time. ( Only 1 clip can play per Audio-source) <-- That's a good thing.

I also have the buttons hooked up temporarily and rather ugly just to test stuff out.

2 loops per instrument at the moment. But when I click the buttons and try to sync stuff up its always just slightly out unless I am prepared and press the loop buttons before the downbeat or upbeats.

Is there any way of creating some sort of clock in the background or a timer so that loops only play after a set time so I could click a loop and it would sync up with the other loops?

By the way!

All loops are at 120 Beats-Per-Minute and last 4 bars so each clip lasts 8 seconds.