If I was ordered to stay in a certain county, how will it work if I was offered a better job elsewhere?

In most states, courts permit a custodial parent to move out of state with the child if the parent has a legitimate reason for the move (as opposed to a bad faith reason such as merely wanting to get away from the non-custodial parent). And relocting for a better job has been deemed to be a valid reason. Thus, non-custodial parents who seek to prohibit the custodial parent from moving are typically unsuccessful.

The reason for allowing the custodial parent to move with the child is that it is unrealistic to assume that they should be required to reside in one location for an extedned period of time, especially since the non-custodial parent is always free to move. In other words, the custodial parent should have an equal right to move. Additionally, courts routinely allow the custodial parent to move with the child in order to discourage relitigation of custody.

That having all been said, the courts consider whether the move is in the "best interests" of the child.

Without any more facts, you probably are the parent with the right to designate the child's primary residence, and you are referring to a geographic restriction in a parent-child relationship order. If you simply ignore the court order, you may be held in contempt. The only way to change the geographic restriction is to go to Court to request a modification in the current order. It is best to contact an attorney about your specific situation to discuss options.