I was wondering since both the ground and neutral are connected at the box into the same ground bar can you use a jumper conecting the grount to the neutral in the outlet box? Will this give you a grounded outlet?

No, using the neutral as a ground at a device such as a receptacle is not allowed, ever. The only method to ground a receptacle properly is to run a new cable with a ground wire.

But if both neautral and ground are connected to the same ground bar in the pannel box why can't they be connected in the outlet box ? What can happen? Where the outlet is located in my house I would have to take the wall down to run a new wire

Frosty...
First, making any connection of an equipment ground conductor and a Neutral conductor
Anywhere other than at the first overcurrent protection device is not permitted by any electrical code...
The equipment ground conductor is for safety and not for conducting normal current.
There are unusual conditions, sometimes hazardous, created when Neutrals and Grounds are connected incorrectly... circulating currents or a hum and static...

Please try to connect these conductors correctly... if you have an issue describe it and
Maybe there is a way to do it correctly.

I see this is a reply to your other thread. You should have just posted an answer (reply) in that thread.

Like you were told, the fact that they are both on the same bar make NO difference. Yours is a common and highly misunderstood, yet very incorrect thinking.

It's what the wires do once they leave the panel that matters.

The neutral carries current, the ground does not. By connecting the neutral to ground outside the main panel it exposes bare and exposed metal parts to potentially dangerous currents. THIS is why there is a separate ground and neutral at each device. The neutral carries the circuit current, the ground is a safety backup.