Synchronize motion with an external event

Hello! First time poster here.

I have a situation where I need to synchronize a series of motor positions with an external timing event but I can not precisely control when the external event will happen. I can send a series of pulses to the PMAC for synchronization but I'm not sure how to make sure everything is in sync. I have already written code to do this asynchronously but I didn't have to worry about the timing in the initial setup.

More details! I have a series of X-ray pulses (~100 but it varies) that need to hit my sample at specific positions (~0.2 mm apart but that can vary as well). Each X-ray pulse has to hit a different spot on my sample. The pulses come at a rate of about 10 Hz. The motor motion is usually just linear and I want it to be a continuos motion through all of the motor positions. I know that a stepped motion would be easier to implement but I have problems with sample vibrations that limit my speed to 2 or 3 Hz.

I'm thinking about sending a separate pulse train to the PMAC that will provide the timing of the pulses and then send a different pulse to actually trigger the motion. I'm just not sure how to do the synchronization.

I have Turbo PMAC2 if that matters.

Thanks for the help!