I am creating a lower third bar, with scrolling text moving from right to left. The bar fades out into the footage toward the right hand side. I want the text to also fade on this edge as it scrolls in, so the text isn't visible on the footage before the gradient is at 100% opacity. Not entirely certain if this makes much sense. A still from the video can be seen here, hopefully this will clarify what i'm trying to do.
Pre-comp the text layer after you have done the animation and you are happy with it and draw a mask on the right (a rectangle) up to the mid point where the bar fades. Apply feather on the mask to match the fade.