There was a couple of cases here like that in Oklahoma.  When it was boiled down the Employer could not force someone (through a contract or other agreement) to no be able to practice his/ her trade.  This would be like telling a doctor that he couldn't practice medicine if he went to another hospital.

As for me, my employer wanted me to sign a piece of paper like that and I threw it away and refused to sign it.  He was pissed and I was ready to fill my box up and leave over it.  He backed down, I got a raise, my next project earned the company a couple of Mil.

Now if you are employed by them then they own the design you make on their equipment and time.  If you have your own equipment and are off the clock then things can get fuzzy.

Carl Bright (CMC) Communications Mfg. Co.
cpbright@ionet.net
www.ionet.net/~cpbright