scrolling text speed

I'm trying to create closed caption text (in Motion) that will display one line of text at a time as the subject speaks the line. I've tried masking, changing text clip lengths, editing in motion, changing margins for text and can't find a way to adjust the text across the bottom of screen. The Scrolling Text in Final Cut is very limited in selecting a smaller area, adjusting speeds other than adjusting the title clip length and editing in Motion has given me control over the area of text that is displayed, one line, but not as much control over speed.

I would like to be able to have a mask over text, that displays across the bottom, where I can scroll the text manually for each sentence resulting in a Closed Caption over the actress.