Text Box Control Behind Object

In After Effects I want to have text slide right and disappear behind an object without reappearing on the opposite side of the object. I can get it along with the text/shape box slide behind the object. No problem. But it reappears on the opposite side of the object. I want the text/shape box to collapse against the right side of the object box as it disappears behind the object. How can I anchor or get the right side of the text/shape box to hold in place without having to add multiple key points to stop the right side from move too far? Do I need to write expressions to get the right side to hold position?