is your MPC synced up with Pro tools?
if not, You'll have to make a selection of 4 bars and use IDENTIFY BEAT in the Edit Menu. just make sure to get a Perfect loop before you use Identify beat. then Pro tools will make the tempo & grid. If the Tempo matches your original tempo or even close, your good. Just use your ears. Then you can just ALT+R to bring up the repeat function. then type in the number of times you want it to repeat. or you can CTRL-D to duplicate it once, or just keep hittin CTRL-D until satisfied with the number of duplicates.
I'll make a tutorial if you like, So you can see it in action. then I'll set-up a link to it.
-Friction