Sending external program changes : Placement?

Hello! I'm working on an mpc500 and sending program changes to a Korg er-1 drum machine to control my beats and sending midi sequences to a microkorg for melodies. I love this setup! I've figured out how to send program changes to the er1 and to have them recognized, but if I place the change into the first note of the bar via the step editor the sequence, the er1 has to cycle through at least once until it changes over. Any way to have my changes registered when I change the sequence on the mpc?
Thanks! This is my first post here. I'm very happy to find this community and look forward to corresponding and sharing inspiration!
Best, mowwow

I;m assuming here you have the mpc and the ER1 in midi sync rather than just triggering it's sounds.
If you arrange your sequences on the mpc in SONG mode and add an extra blank sequence of one bar to the very start.
Now do the same with the ER1. Add an extra blank one bar sequence to the start.

Then when you start the mpc, the blank bar will play first on both machines before the first proper sequence starts. By then the two sequencers will have had time to lock together and the ER1 will read the program change at the head of sequence one as it should.

Thanks! I'll see if I can get that working. I'd like to have many pattern changes sent to the er1 within the course of a performance though. It seems the easiest thing might be to record the 16 step midi patterns from the er1 back into a new track on the mpc, and to trigger the er1 entirely from the mpc, as opposed to just sending program changes. Or, maybe I could shift a program change so it comes slightly early... Or place the program change on a muted track earlier in the previous sequence and unnute it before the change to the next sequence.

I'd be inclined to map the MPCs pads to the er 1 (or just work out which pads correspond) and just trigger the sounds directly from the sequencer in the MPC.
Then you can keep all the programming in the mpc and just send program changes to change drum kits on the er 1 (I assume that's what your program changes are for).
It would make for a streamlined workflow.