Wire colors to a switch
No Jamie, in your illustration, the white would be re-identified at both ends and hooked to the source black to feed the switch.
Short version of what the '05 NEC says...
200.7 Use of Insulation of a White or Gray Color or with Three Continuous White Stripes.
(A)General. The following shall be used only for the grounded circuit conductor, unless otherwise permitted in 200.7(B) and 200.7(C):
(C) Circuits of 50 volts or more.
(2) Where a cable assembly contains an insulated conductor for single pole, 3-way, or 4-way switch loops and the conductor with white or gray insulation or a marking of three continuous white stripes is used for the supply to the switch but not as a return conductor from the switch to the switched outlet. In these applications, the conductor with white or gray insulation or with three continuous stripes shall be permanently re-identified to indicate its use by painting or other effective means at its terminations and at each location where the conductor is visible and accessible.
I can post the rest of 200.7 if anyone wants to see it...I just didn't want to bore y'all...that bit was bad enough.
In a nutshell...you can only do it with cable (or 200.7(C)(3) is an app for cords), not conduit methods. If the white isn't going to be a neutral as part of the loop, you re-identify it and use it to feed the switch.