Defendant keeps moving on me!

What is the name of your state? Michigan

I'm trying to take an ex-boyfriend to small claims, but he's moved twice on me. I found him the first time, but when the court officer went to his residence to serve him, his roommates said he had moved, which he hadn't yet. Now he has moved. I know the general vicinity of where he's at now, but how can I find him? Can I file and have him served at his work since I don't have an address?

Yes, or you can tell whomever serves him to get a faster car.

" Can I file and have him served at his work since I don't have an address?"
*** Yes. Or you can contact the court about using 'alternative service'.