Abstract: A software tool generates computer program code in a message based environment. The programmer interacts with the tools making a number of selections to define the user interface of the computer program. When this is complete the tool analyses the user interface definition and produces a list of all the messages that could be produced by that user interface. On the same display a list of blocks of code from a code library is shown. The programmer selects a message and a block of code to be invoked by that message. If the block of code has any prerequisite requirements, the programmer is prompted to meet them. A message identifier, a pointer to the code block, and any prerequisite data is then stored in a linked list structure. When the connection process has finished, the code for producing the defined user interface is generated and the list of connections is traversed, resulting in output the blocks of code from the library in the correct place for their corresponding messages.