Please, draw a picture of what the user will see. Your description (post #5) sounds like you need an unknown, but infinite, string of lights, with only one light per word (but I think I might be wrong, since infinite is not easy to program).
I have made something similar to your needs. It lights a selected number of LEDs for a selected duration. You edit the "sequence" of steps, set the "duration" for each step, and set the "speed" for a synchronized display. The application was a "lightning" simulator for a diorama.
Here is the link to the code and the data for the simulation. Ask me anything.