A terminal coupled to an intelligent telecommunication network may invoke dynamically modifiable subscriber services by transmitting information to a switch to which script files, each containing programming script needed to initiate a calling feature or other advanced subscriber service and a criteria statement used for triggering execution of the programming script, were downloaded thereto from a home location register where the script files may be added, deleted or otherwise modified by a system administrator. A program execution module residing at the switch compares the received information to the criteria statement for each script file downloaded thereto and executes the programming script of the script file having a criteria statement which matches the received string of digits. In wireless systems, the script files are downloaded to an MSC whenever a roaming terminal registers therewith.