it's not clear what you want to do but you can use actionscript to mask objects.
To hopefully make more clear, there’s a piece of text I want to mask with the background. Like my background is waves and I want to mask that wave background onto my text. And besides dragging my text layer underneath my masked background layer, I was wondering if there was another way to accomplish this.
duplicate your waves and use one copy for the background and one for the mask of your text.