Fully agree with St Lunatic, do not drive the car until you have that fixed.
It sounds like the valve body on the box has gone, which will be expensive to fix, but it can be fixed with the box still in the car, and should be about 3,000 to 6,000 to get done. However if you drive it further, you run the risk of damaging the internal clutches, which is a 15 to 25k to fix.
Anf if you must drive it, say to the repair shop, avoid traffic at all costs, if you cant do that, spend 500 bucks and have it trucked to the shop, or....
I may however be completly wrong, and your box is dead already, lets hope not
who's going to say it, should i ?