I have a dual core 2.26 ghz macbook. Could anyone help me out with ideas on how to run this?

I'll second the request - if out of idle curiosity, since my solution was to build a high-end gaming PC and quit fighting hardware that was not only several years out of date, but portable (and therefore underpowered to begin with).

I could find no way to run ArmA on my MBP, which is the same model as yours. Even with every last graphics option set to its lowest possible value, it was unplayable anytime there was a plant on screen, which is usually, and anytime I used a scope. The first problem can be somewhat mitigated with this mod, which replaces the vegetation with OFP:R models, but the second remains totally unsolved.