This is what I've done with my N97 and N95, when in the pocket and a ring comes in, I do a mild double-tap to the back of the phone. This stimulates the sensors measuring for the "flip to silent feature" and boom I'm silenced (or in the case of my N95, I've silenced the call and sent an SMS that I wasn't available). Try that and see what happens for you - just not in another meeting ok.