Either/Or Select Options

[curtiss]

I'm setting up a couple of selectboxes within some forms I'm working on. The selectboxes are set to allow multiple selections. I'm curious if there's any way to have one select option that, when selected, does not allow you to select other options in the box.

I know I can do a "Select All" type of button with javascript, but I'd really like the "All" option to be a completely separate option within the box, as I want it to have it's own unique value, rather than just adding all of the currently available options into an array. However, if someone selects the "All" option, there shouldn't be any reason for them to be able to select the other options in the box.

So, basically, I'm looking for a way to make one select option disable all of the other select options in the box when someone selects it.

Any thoughts? I'd kind of like to do this without javascript if possible.