First thing you do when they post:
-check value of a session variable called lastPost (of course, it could be anything, you make it up)
-it has a timestamp and if it's less than X seconds in the past reject the submission
-otherwise, set lastPost to the current timestamp and allow them to continue
Or maybe I'm misinterpreting what you want (I was thinging just no reposts within a certain amount of time...)
If you have a set workflow and you absolutely do not want them to repeat part of it then this is something that should be built right into your workflow without too much extra trouble. More or less, you have some form of recorded state about where they are in the workflow which would include if they've posted form X already. If they post form X again, you're looking for form Y data and it should be obvious that that's not what you're getting. Then you either kick them up to form Y with an error message or do something else to punish them. I guess I'm more or less describing what you said you don't have time to do, but if designed in from the beginning, I don't think it'd be much extra work.
Does any of what I've said make sense?
