Abstract: A variable computer icon on a display functions as a single control for a data processing system exercising a complex software function using multiple parameters. As the single control is varied on the display by a user, the response of the complex software function due to automatic parameter changes is varied. Moving the single control in one direction increases the response of the function. Moving the single control in the opposite direction decreases the response of the function. A method is provided for generating settings on the icon to provide smooth, gradual transition with consistent behavior of the function between S.sub.min, the minimum position, to S.sub.max, the maximum position, on the icon. The single control provides ease of use, simplicity in controlling the execution of a complex software function along with a reduction in space consumed by a graphical user interface and the ability to alter the underlying function without any apparent change to the interface.