You dont know anything about mice do you
They 'follow' pheromone trails which have piss in them because they are essentially incontinent little twats. The ammonia smell in the urine of all higher animals is urea, smells like ammonia, but it's not ammonia.
I'm quite aware of how it all works, prick. However, either I heard an ole wives tale or got it confused. According to eHow, it drives them away...
http://www.ehow.com/how_4457403_get-rid-mice-ammonia.html
So there, it does have an effect on them! I (SORTA) WIN!