Change Status of person with order

Change Status of person with order

I need to change the status of a person based on an order. Eg labours field i have five labours ( 1 2 3 4 5)that have status "free" in radio section. While booking an order for a labour if i choose 3 inlook up field i would like his status to automatically change to "occupied"

Would really appreciate if anyone could help me with this.

Rachit Agarwal