1. Build this.
2. Remove the pressure plates on the outside, but leave the ones on the inside.
3. Place the button wherever you want it.
4. Run a wire underground from the button to the redstone below the pressure plates you removed.
The place where I want the button is on top of the redstone torch. So, that won't work. I'll do some more tinkering, though.
The Troll inside me wants to come out. But I'm Holding it back.
That's a small one tick door opener.
Combine that with (Not my design)
and hook it up to a button and tada you have what (I think...?) you want. =)
So you want the button to enable/disable the pressure plate or do you want a button on the outside and the pressure plate inside?
The first one will require a toggle and an AND gate. I don't have access to my saves right now but I have a save with this setup. If you want to see it.
The second just uses an OR gate. Both the button and the pressure pad are wired to the doors. You have to make certain the button is a block away from the doors though otherwise it'll open the one it's next to. Same with the pressure pad. Walls are going to be three blocks thick if you want to keep the wiring hidden.