Ticker Text in Square motion. how-to?

Hey all,

After some extensive research on the net and the usual websites, I couldn’t come up with a solution for this problem:

I’m trying to create a scrolling newsticker type text, which scrolls in a ‘square’ and not only horizontally across the screen.

The text should be correctly readable when it scrolls across the lower side of the square and then just scroll along the left side of the square and when it reaches the top of the square, scroll from left to the right (flipped on its head), then scroll along the right side of the square to dissappear, where the text originally startet.

The whole scrolling thing should be running continuously, with a fixed text, so no fiddling with dynamically loaded text needed.

Has this been done before?
Could you point me in the right direction? Is there maybe a component or script with which I could work?

Any help is greatly appreciated.

cheers,
dual