employer won't activate benifits

the company that i work for has an investment program that any one that has been employed for 2 years is eligible for. i am starting my 4th year there and every time i ask my boss about signing me up he makes excuses and says that he'll get to it. how can i get him to quit stalling and am i entitled to any money that should have been invested over the past year?
thanks,
yp