Air as a second screen

Hi everyone,

i need to use may macbook air as a second screen for an Imac.

I connected with thunderbolt the 2 machines and i can use the IMac as a display monitor for the MBAir...and it was easy and simple(just click cmd+F2 on the keyboard of the IMac). But i cannot do the opposite.

it seems that the cmd+F2 does not work on the MBAir..

Does anyone have a solution for that?

Thanks!

L