I'm looking for a way to prevent successful persuasion of a particular NPC ( not a generic prevent for all NPCs). the idea that you can use a single sentence of sweet talk to cause an NPC with a disposition of 20 to suddenly love you is ridiculous, and I want to prevent it or mitigate it if i can.

I thought of using a moddisposition -X in the results, but I'm unsure how that would work out with the engine just raising disposition, and also since the results of persuasion are variable, it's hard to say what would be a good number to use. Persuasion results seem to run from 10 to about 50, but setting a minus 50 then having the PC get a plus ten would not be fair for a successful result.

I could write a script, but since the results would not occur until the end of the conversation, life would be very tricky for the player. I suppose using goodbye after success then running the script would work... but it seems a clumsy work-around. Any ideas?