Get VSYNC from DVI on NVIDIA card

I need to get VSYNC from the graphics card (GTX285) to the controller of some old 3D glasses I have. When I was still using CRT, I would simply tap pin 14 of the VGA connector.
But I’m having a problem with LCD now. I know DVI has an analog VSYNC pin, but from what I can tell it’s not activated if the monitor connected is digital. So how do I get the VSYNC signal then? I could use the second DVI port and hook up an analog monitor to it and set the same refresh rate and hope the two outputs are synchronized, but I no longer have an analog monitor available, and the graphics card seems to not produce an output on a port that’s not connected……or-present.html

Not to mention that LCDs may introduce a delay befaore displaying a frame, it can be anything from 0 to 2 frames and any fractional in between…

I’m going to try the dummy adapter method. I just hope that the two ports on the back can be synchronized without drift between them.

ZbuffeR, I’m aware of this, but I can always add an adjustable phase delay on the input to the controller using a variable capacitor that costs a couple of dollars.