With the B2, the answer is "not really". You'd need to have programmed that setting in beforehand and swap to it using presets in the unit. Or, you can go into edit mode within a patch and click back/forth on the switches to turn a specific effect on/off. When I was using my B2 live, I found the overall tone I wanted and then programmed that sound with additional effects into the presets above and below the "reference" tone (e.g. B1 is my tone for pick playing, B2 adds a pitch shifter, B3 changes to a chorus.)
I've since moved up to the B9.1ut which allows you to turn specific effects on and off with just a tap of a footswitch and couldn't be happier. I have my X-phaser, pitch shifter, chorus and reverse delay settings instantly available and simply move down a preset if I want something else (slow motion, autowah, etc.).