Giving users simple access to QoS selection capability of ATM networks is important for the future of integrated services networks. We describe the first instance of an application in which users had the capacity to tune ATM traffic parameters with a button, at run time. To achieve this we implemented the necessary signaling extension on ATM switches as well as on end-systems. Furthermore, we extended Arequipa (Application REQested IP over ATM; a mechanism that enables applications to request direct ATM connections for their exclusive use and to directly control their traffic parameters) to support modification, and modified the popular Mbone tool Vic (VIdeo Conferencing) to use Arequipa to request and modify ATM bandwidth at will. We describe how Vic accomplished this over the ATM WAN of SWISSCOM, transferring live video from Lausanne to Basel over switched, renegotiable ATM connections.