You can do this by creating a new EVENT task (another 100 programs), and triggering it with an EVENT instruction. There's no need to lock it to a periodic execution rate that is asynchronous to your other continuous task programs.
200+ equipment phases for S88 batching, plus programs for supporting equipment. Using Phase Manager already eliminates overhead. Having 1 continuous task and 5 other periodic tasks doesn't make sense, just have them all has periodic tasks. Then the Task Monitor tool actually becomes useful in helping you identify logic/timing which is taxing the PLC.