Exploring AI with a goal

What i want to do, is to make a bot explore the level, lets say a large network of 4-sided rooms with doors at each side. But the level will have a goal of sorts, a treasure chest or whatever, and bot knows its general direction. How do i set some kind of variable, so that i could change bot's "determination" ? So that with one value it will only go through doors leading "north", and with another value it will choose other doors unless it already went through several doors leading "south", then it will return at starting point and choose a different route.