I think there's no way to do that. The reason is because, for interlaced mode, the dongle has a line-blanking function built into it's hardware but it doesn't have hardware to produce a "checkerboard-blanking" function. That's what you're looking for but wait. I heard someone cracked open an xforce-3d dongle and found a FPGA. Maybe it could be reprogrammed or replaced with another to do the job. No, that's not likely since each row of pixels is analog and so it would be hard to get a handle on alternating pixels especially with varying resolutions. Maybe someone could make a custom dongle to do the checkerboard-blanking with a digital video signal. Anyway, next idea...
What about that Overlay feature I've seen in the nvidia drivers? Could someone make two complementary checkerboard patterns with alternating pixels transparent and black and then overlay them alternatingly on the screen in sync with refresh rate and glasses? I bet nvidia could do it. Too bad. I think the chances are slim and none and slim just left town. Oh well, you never know, maybe some miracle-worker could show up. That would be pretty cool though. My sense is that it would be a little better than interlaced for reading text but I could be wrong about that.
Wait, if you could just get one checkerboard overlay on screen at a time, then you could at least verify that the driver works. Use your printer and a transparency, then vibrate it (or your head) in front of the screen at the refresh rate.
PS: I smoke rolled-up paper 3d glasses.