Arc text

I have a question in regards to dynamically produced arc text and was hoping someone could point me in the right direction? I need to have the text arc as Voetsjoeba does at http://www.voetsjoeba.com/lab.php?i=3 but i need it’s arc to be limited to the number of characters on the shirt…kind of like it does on a football shirt…well exactly as it does on a football shirt. With Voetsjoebas example if there is only a small amount of character then the letters are distributed over the entire 180 degree curve. I need to have the letters start from the top and reposition themselves outward depending on the number of charcters in a string. Basically somebody is going to add numbers into a field and thoes numbers will show up on the back of a football shirt onChange?

Any ideas about how i could approach this would be much appreciated

Sam