Duplicate Orders

Does anyone know how I can disable the Submit Order button on a onepage checkout after it has been clicked once? I can't even seem to find the file this is controlled at.

I have had a few customers become impatient and click it twice which causes a duplicate order.

This is caused typically by the SQL server being slow to respond.

Hmm… Well that doesn't sound good. I need some way to lock the SUBMIT ORDER button from being clicked twice then. I have optimized my CSC install as much as possible and it performs pretty solid except for the slow downs every now and then on checkout which cause the customer to want to click more than once when submitting an order.