Setting Employees Sales and Repair Goals

I give each one of my employees an evaluation every 90 days and at their 9 month evaluation I gave each ones goals they must accomplish—letting them know X amount covers their individual wage and X amount means they are making money for the company. I gave each a repair and a sales goal—reminding them individual goals will go up at their one year evaluation. The other day I was considering setting product goals as well—meaning X employee needs to sell X amount of diamond studs this month or X amount of Scott Kay, etc. Is that something any of you have done?