dynamic velocity scaling?

This question will probably reveal my profoundly bad mathematics, but...

I sometimes scale my velocities down to a range of 0. to 1., and multiply the output by itself, so that 1 still equals 1, but 0.5 = 0.25, etc. This gives a nice curve to the velocity response.

What is the best option to put a variable on this, so that i could scale it in real time, so at one end of the spectrum all velocities are the same, and at the other end, you only hear the full velocities?