We describe a general method of calculating the fully differential cro
ss section for the production of jets at next-to-leading order in a ha
dron collider. This method is based on a ''crossing'' of next-to-leadi
ng order calculations with all partons in the final state. The method
introduces universal crossing functions that allow a modular approach
to next-to-leading order calculations for any process with initial sta
te partons. These techniques are applied to the production of jets in
association with a vector boson including all decay correlations of th
e final state observables.