Don't worry Jude, easily done! I've given you your own new thread.
Being a Mac, you can give each monitor it's own profile, which is great. I ran a ACD on my Mac Book Pro for a long time.
First, pull the window onto one screen, and run the calibration. I'd go for the Advanced option, as you'll want to pull down the brightness to about 12' and that'll help you do so. When it finishes, it'll ask you for a name, so call it something sensible!
Now open it again and run it on the other screen. I used to find I'd have to drag it to the other screen, quit and reopen, before it would run on the right screen. Quite odd! :roll: Do the same Advanced on that one, and then give it a sensible name.
Once you've got profiles for both, open System Preferences > Display and check that the correct profiles are assigned. Hey presto, you should be sorted!
You will probably find that your MacBook Pro screen won't absolutely match the ACD - laptops screens rarely are a perfect calibration.