If you don't want a button but just want the key to do something, then simply adjust the button's position until it's off the dialog.
Personally, I prefer to hide a button in that situation instead of placing it off of the dialog. It just seems cleaner that way.

Anyhow, here's an example part of a dialog:
button "&Ok",20 20 20 10, ok
That will allow you to press Alt-O inside the dialog to activate the button.
Here's one more example:
button "Open &Log",20 20 20 10
That will use Alt-L to activate the button. The & can be placed before any letter in the text.