I have a workaround. Load all your loops to lets say the static (or flex) sampler slots 1-15 leave 16 empty. Set up all your samples in the editor at the ATTR page to quantise trig. (you have to scroll all the way down to the bottom of the page to find it). I set it to 8/16. Now go to your track and press the function key with the arrow down key and select the slots option. All your trigs will turn green except the the 16th trig. Thats your off trig. press play on the OT now you can launch sample loops quantised in step with the sequencer and the loops can be turned off by pressing the 16th trig. 