Need help with numeric entry please!

Hi,

I have a silly idea..

I have had a running joke going through a course, and the denouement of the course is that I allow the "other voice" / learner to do this.

I need to tell learners to enter a "launch code" into a numeric entry box.

When they enter it correctly - the state of a really large button changes from inactive to active ("normal"), and they can then press it to go to another layer and run a video of something very large going "BANG!"

I have everything in place except the slightest idea of how to do the numeric side of this because numbers scare me and are evil...

Could someone please help me out with how I would do this?

Thanks

Bruce