I would create a Color Matte (Or use the Lower 3rd option in the Text section). Add text to taste, use crop tool for color matte is you didn't use lower 3rd option. Nest them together. Then add keyframes say at 30 frames to the crop option in the motion tab. Go to frame 0 and move the crop sliders and so the right gets cropped off. It will animate the bar and text onto the screen when you play it. Have the additional text devolve on. Repeat crop keyframes to have it come off. Hopefully this helps. Best of luck.