Simple LTSpice simulation

I am trying to simulate 3-phase synchronous rectifier. I have already created source, rectifier and load in LTSpice. I need MOSFET triggering logic. Normally, each of the 6 MOSFETs conducts for 120º. I would like a logic so I can set them to conduct at any value from 0º to 180º (all of them should conduct at same value, so it is not needed to set this value independently for each MOSFET, but one value for all 6 of them).