I need some mathematical / programming pointers, if someone could be so kind.

I would like to program a thing where people can specify their preferences for how many M&Ms they like to eat per day (a minimum number, maximum, and ideal amount), then I can put in some number of M&Ms and see how ideal that number is based on those preferences.

The problem I am having is that I would like the preference distribution to be smoothed out a bit with some kind of gaussian-like curve that may be asymmetrical, and I don't know how to do it.

Can you help?