Probability distrubution to randomized sampling conversion?

Question

Given a probability distribution P(x), how do you come up with a function to use random numbers to generate values for x which obey that probability distribution?

Let me clarify:
I need to program a generator to come up with random values for v so that, plotted on a histogram, they look like the Maxwell-Boltzmann distribution.

Answer 1

These come in "canned form", and are incorporated into spreadsheets that have been pre-loaded into a PC or a similar program that you have added. You may find one floating around in free-ware type web pages. Back in the ancient days, they came with probability packages for use in BASIC or FORTRAN.