Existing resource brokers for computational Grids only focus on locating a machine (computational resource) within a cluster that has the least load. Such simple brokers are ineffective in commercial and complex environments where negotiation over price, time and service-level agreements are required to establish a contract before users are authorised to use a computational resource. This paper presents a brokering system, utilising the Job Submission Description Language (JSDL) standard and extends the Unicore/GS Resource Broker, that extends brokering with scheduling (resource availability) and simple pricing policy management. The brokering system improves the effectiveness in negotiating contracts for the use of computational resources on the Grid. The architecture and implementation have developed a plug-in for Unicore/GS Resource broker and integrates an externally hosted calendaring service to support the described functionality, and demonstrates the feasibility of building systems by composing autonomous services hosted on the network.