If you're derivatizing an amino group, you could use the succinimidyl ester instead of the chloroformate solution. Additionally, if you want to use the chloroformate solution, it shouldn't be necessary to use it in such a whopping excess. 5 eq in DCM should take care of it....
A cheaper reagent in general for derivitization would be dansyl chloride, which is used all over the place...