Strawberry Tree Incorporated is one of several manufacturers of input-output boards for the Macintosh computer. The Analog Connection Workbench program (Strawberry Tree Inc.) provides an icon-based programming system for these input-output boards that has most of the functions that are necessary to implement behavioral experiments. However, experimental psychologists may frequently encounter needs that the Workbench program cannot easily meet. Because the Workbench is programmed in C, whereas many psychologists are more expert in programming in Pascal, we describe, in tutorial fashion, how the user may define new external functions in Pascal on the Macintosh and integrate these functions into the icon-based Workbench programming system.