In a cable network providing, among others, interactive video services, data cells carrying real-time data concerning, e.g., trick mode commands (pause, rewind and fast-forward) initiated by a user are instantly transmitted to a headend facility for immediate processing. The invention is premised upon a recognition that such real-time data typically does not fully utilize the transport capacity of the data cells. In accordance with the invention, non-real-time (NRT) data to be transmitted to the headend facility, although accorded a lower priority than the real-time data, is inserted into those underutilized data cells before their transmission, thereby fully exploiting the transport capacity of the data cells.