We present an approach to the bid-evaluation problem in a system for multi-agent contract negotiation, called MAGNET. The MAGNET market infrastructure provides support for a variety of types of transactions, from simple buying and selling of goods and services to complex multi-agent contract negotiations. In the latter case, MAGNET is designed to negotiate contracts based on temporal and precedence constraints, and includes facilities for dealing with time-based contingencies. One responsibility of a customer agent in the MAGNET system is to select an optimal bid combination. We present an efficient anytime algorithm for a customer agent to select bids submitted by supplier agents in response to a call for bids. Bids might include combinations of subtasks and might include discounts for combinations. In an experimental study we explore the behavior of the algorithm based on the interactions of factors such as bid prices, number of bids, and number of subtasks. The results of experiments we present show that the algorithm is extremely efficient even for large number of bids.