Well there you go you see. I've never delved into the world of motive code in the past before so I wouldn't know what the range was. I'll give it another try with your info and see what happens thanks.
ETA: After messing with the values I found out that the first code snippet above deals with the motive value at which the Sim should stop performing the action. The second snippet deals with the motive value at which the interaction becomes available.
So to get the urinal working I needed to set the second snippet to -100 so that now the urinal can be used at all times and Sims use it until their bladder motive is 100% recovered.
I think that's everything that I needed to fix now. At least I hope it is.