Control Output Voltage on USB Cable Programmatically

[omidomid]

I'm looking for a way to control the output voltage on a USB cable through programming. I don't know too much about how to program USB devices, but I know there's a default 5v output, a ground, and two data lines in every USB cable. Ideally, I would like to be able to set this voltage output to anything, or make it switch on/off with a given frequency.

Any help is appreciated!

 

[dlgoff]

Here is a http://www.delcom-eng.com/downloads/USBPRGMNL.pdf" . Maybe this will help.