D80 and 40D Exposure Modes

[Guido]

I want to attach a completely manual lens to a digital camera and have the camera set the exposure. Think 500mm F/5 manual lens or a microscope.

From what I've read, I believe the Nikon D80 will just lock up. The manual for the Canon 40D intimates that I can set a manual mode and it will adjust the shutter speed to set the exposure.

Can anyone give me any information on whether I can do this? (or if you understand my description )

Thanks.