as you follow the advice from my distinguished colleague kolyur, remember that you'll probably need to be "offline" to make the change – and then "download" the modified program to the processor ...
as for the IOM – it "does its thing" when the rung that it is located on gets executed ...
explanation:
suppose that a "true" OTE located on rung 10 has just changed the contents of an output bit/box to a status of ONE ... normally that ONE status would not be sent over to the actual output module until after ALL of the ladders had been executed ...
suppose that "wait-till-the-end" delay (short though it may be) is still too long for your particular process ...
so ...
suppose that you program a "true" IOM on rung 11 (the next rung in the ladder) and suppose that you correctly address it - and mask it – for the output module and bit "of interest" ...
in that case, the status of the output bit/box would be sent over to the actual output module AS SOON AS THE IOM GETS EXECUTED ...
no offense intended, but if you have any trouble understanding that description, then you probably have misconceptions about the differences between OTEs, outputs, and bits ... (believe me these are common problems that often confuse even experienced technicians and programmers) ... if this sounds like part of your problem, then the YouTube videos on the Sample Lessons page of my website should be very helpful to you ... be sure to watch them all IN ORDER since each lesson builds on the previous ones ...