How can I create text that stacks up at line breaks rather than drops down?

I’m working with design restrictions where text can build upwards, but there is a defined bottom border.

I’m looking for a setting or an expression that stacks the text upwards after every line break, instead of the default where text drops below the original line.

I tried the expression from AEscreens.com but it doesn’t seem to be working for me. When I try it, it simply centers all the text vertically.

I want the bottom-most text line to stay at a set y-coordinate.