After effects masking question

Greetings, everyone. Question about After Effects (specifically 7, I haven’t been able to get CS3 yet, sadly). Is there a way to do group masking a la Flash? I’ve got a lot of experience in AE but I still haven’t figured this out. I have sequences where a lot of different clips need to be masked by one stationary mask. I don’t want to mask each individual clip, it’s just too inefficient! Is there a solution, or a workaround, like “anchoring” a clip’s mask so it doesn’t move with relation to the clip it masks?