If all of them are picked, (you didn't filter any out with events,) it should still work on all of them. "For each" is assumed.
I would be 100% sure of that if I hadn't just read Justifun's suggestion. <img src="smileys/smiley4.gif" border="0" align="middle" />
Edit: I see, you meant you do have some filtered? It works the same way as a system version would, they both act on what is picked. (all top events start with everything picked, and you filter down to the ones you want to work on. However you can use "Pick All" to reset the picking list.)