A system for generating a requisition comprises a client computer system and a server computer system connected via a network. The client computer is configured to allow a plurality of users to access the server computer system. The system further includes a server application comprising a user interface running on the server computer system and having a multi-tier architecture. The multi-tier architecture includes a first tier of client application code for initiating processing by the server application in response to input by a user of the client computer system, a middle tier of object-oriented server application code, and a third tier of shared access and data code. An application programming interface is configured to allow a user, such as a system administrator or the like, to customize the user interface. In a further aspect, a method of customizing a server application is also provided.