High Score Name entry

How would I allow the user to enter a string of a specific length? I have the scene made and the buttons to exit, I simply wanna make it so that the user can enter there name or any string for that matter, I even have the rest of the code made for after he enters the string I just want to know how to allow / disallow the user to enter a string and possibly limit its length

This should help ... http://unity3d.com/support/documentation/ScriptReference/GUI.TextField.html