Easy mask question

[FilmMagic]

I'm working on a new project in after effects, and have a simple problem using masking. I have text animated, just dropping from the top to the bottom of the screen, but I only want it to appear after it passes behind another shape. I created a mask on the text, but for some reason, the mask is already animated to follow my text.
I want the mask to stay where it is, set to 'subtract', so my text will be seen only when it leaves the mask, but the mask is animated.

What am I missing?

Thanks

[Huy Vu]

I think the problem is that you put the mask on over the moving text, so when you move the text the mask also moves with it. To fix it draw the mask over the object that the text is supposed to pass through and just leave the mode to Add.

Or you can set the opacity of the text to zero when it passes through the shape and make it visible again after it has already passed through. That would be easier I think.

[FilmMagic]

Sorry I'm so late in replying jade. That worked great. Thanks.