Text option value : Set to maximum amount of caracters

I am building a backorder system for photos.. Customers can order photos true unique id thats on their pictures..

So i am building a text field for them to enter unique id..

In catalog>product>option>Text>option value.... Can i set the option value to a maximum or fixed amount of caracters for example 8 caracters..

So that customers dont enter 2 id's in this field/ dont enter wrong id ..

http://www.borduurkoning.nl/shop/groeim ... lila-paars

ann example above

V1.5.1

Thanks for any replie