Check Engine Light on 1994 Volvo 780

Two weeks after I had a 100K mile checkup on my Volvo, I started getting check engine lights. I never had the light to come on before I had this service.

Not only did I have that light come on 2 weeks after the 100k mile service, but again a week later after I had it serviced for the check engine light and AGAIN (second time) and again (third time) in the span of about one month from 100k mile service.

The Volvo service group is telling me that this is normal for a car over 100k miles and that there are 95 prompts from the engine that can spark the check engine lights. Each time I've been charged over $100 to put the check engine light out.

I believe the service department is incompetent :evil:
Is it possible that a competent service person could make a complete check so that I'm not taking my car back every week for a check engine light---AND PAYING MONEY EACH TIME FOR A DIFFERENT CODE?[Code:1:2d564112c3][/code:1:2d564112c3]