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

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.