How can I turn off the "allow automatic updating" for an app? Once I've checked off the box to "allow automatic updating" for an app in the market, is there any way to undo this without uninstalling and reinstalling the app?

Moto Droid running 2.2

UPDATE:  Apparently I am losing it.  Originally it happened with PDAnet.  I accidentally clicked the checkbox and as soon as I did the option disappeared.  I tried restarting the market, restarting the phone but the option never reappeared.  I uninstalled it and reinstalled it and I had the box back, unchecked.  I was afraid to test it out on other apps until the answers below confirmed that either it was an isolated bug or I was crazy.  Needless to say I have the option to uncheck it now.
On the HTC Incredible I just searched for the particular app in the market, selected it and unchecked "allow automatic updating" from there. Hopefully it works that way on your phone (and others).