LED Dot matric display - Help

I've recently purchased and setup this 16*16 LED Dot matrix shield.

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I bought 4 as seen in the websites description. I've used their example code and can use it easilly to scroll words.

However i'm having great difficulty to get it to do want i want to do.

I basically want a rectangular bar to scroll across the 4 panels from left to right until it reaches the end.

I also want this bar to be able to get thicker (fill up the panels) as i turn a transistor.
(i've got a small file in programming to illustrate this)

It's for a uni project, to simulate how far away a train is and how full the platform is.

If anyone know anything helpful, i'd appreciate it.

as i turn a transistor

Huh?

So start off slowly and try and understand what you have. You can get a display right, so now tweek the code and make it do something different from the demo. I assume the demo is centred around displaying text, some where the ASCII text will be converted into a dot matrix character. This is done by a look up table. Assuming this is in software then hack at that look up table and try and change the shape of the letters. Finally abandon the letters and hack it so it displays the shapes you want in place of some little used symbol.