Changing the Fidelity of a Brush, while you are drawing?

Hello,

This may be an odd question, but I will give it a shot.

When I change the Tolerance (Fidelity) of a brush in Illustrator, I usually go into the Brush Preference and decide where I would like that value to be depending on what I am drawing. Is there anyway to toggle or change the preference to the other direction, while you are actually drawing?
For example,  lets say I have the Fidelity set to accurate, but then I get to an area I would like to be more organic with smoother curves, and I would like to change that fidelity to go towards the smooth area of that option, without having to go back to the preference.

Is that possible?

thanks

Babs