So you want a random combination for your combination lock? That doesn't sound like something you'll ever get open again, but sure you could do that. You'll have 720 combinations to try before it changes.
Get the combination lock working with a hard coded combination first. Once you have that, changing the combination should be trivial.
You have 6 binary switches so the switches can represent any integer between 0 and 63 inclusive.
Every couple of minutes you could generate a random number between 0 and 63 inclusive.
You read the switches continuously and if they are set to match the number before it changes again you unlock the box using an output.
I suggest you use an LED to indicate the start of each time period.
With the time set at 2 minutes you could probably do a brute force attack and run through all the possible combinations.
You could make the game more fun by decreasing the time period after each success. A buzzer near the end of the time might build tension. You probably need some way to get into the box by default e.g. the initial unlock code on power on could be 000000.
This brings up an important question. Does the order matter? Or just the combination?
With switches I was taking it that they just represented a number, like a bicycle lock, so order does not matter.
You could have a lot of fun with this project. If you used a rotary encoder it could be like a dial to a safe with turns clockwise and anticlockwise being important. It could click when you got a digit. If you got really carried away it could click quietly so that you needed to use a stethoscope to hear it