http://www.nikonchat.com/nikon-wireless-remote-d90/

making flash nikon sb-600 as a remote flash, but off the flash of the D90. Is this possible?
I have a D90 and a Nikon SB-600 flash. I would like to treat Flash as a wireless remote flash and turn off the flash with the D90. Is this possible? Thanks
Yes Steps: 1. Go to menu 2. Go to menu custom settings (the pencil icon) 3. Scroll down to find "e2 Flash cntrl for built-in flash" 4. Commander Mode and switch to turn is based on the flash to "-" That's all you need to do. Hope this helps.