I think I see what he's trying to do, e.g., a one-off, I want to fire this m/r on Feb 13 @ 2am, instead of going into the m/r and adding a check (is it roughly Feb 13 @ 2am? if so continue with the m/r, else exit), just being able to set that dynamically via a suitelet or portlet if I'm understanding your use case correctly, you could set a custom record for that date via a suitelet/portlet and have the m/r check that/those custom records to see if it should fire, then delete the custom record when it's done