In a programmer for an implantable medical device, a method for operating and controlling a implantable medical device, and in a computer software product, a graphical representation of a quantity influenced by the operation of the medical device is displayed, and parameters relating to the control of the device are associated with portions of the graphical representation. When an operator selects and alters the shape of the displayed graphical representation to illustrate a desired operational effect of the medical device on the quantity, a value associated with the altered shape is automatically modified and communicated to the implanted medical device. The operator thus is able to select parameters on the basis of the intended effect, rather than setting parameter values and then observing the effect.