D70 bulb shutter setting. Need help (x-post)

So one of the <i>only</i> things (and this is pretty minor) I don't like about my D70 is that I can't really figure out how to take a picture using the 'bulb' setting the way I want to.

It does have the 'bulb' setting, but it works this way:

you depress the button to open the shutter, hold the button down for a while, and then the shutter opens once you take your finger off.

But I want to be able to take bulb photos like I could on my N65, which is like this:

press the button to open the shutter, release the button, go eat a sandwich/take a nap/whatever, then come back and press the button again to close the shutter.

I don't want to hold down the button for hours to get some good star trails. Is there a way to do it the second way I described, or am I just going to have to use my N65 for star trails?

Thanks for your help.