Certain aspects of the disclosure are directed to customized communication lists for data communications systems using high-level programming. According to a specific example, a data communications server is configured to interface with a remotely-situated client entity using a first programming language. The data communications server includes a communication control engine that is configured to provide a private branch exchange (PBX) for the client entity. The communication control engine is configured and arranged to identify client-specific sets of control data derived from instructions written in a second programming language that is compatible with the first programming language, and to control communication routing by determining whether to route incoming data communications in response to a comparison of at least one feature of the incoming data communications telephone communications and the client-specific sets of control data.