Limited Digits in a TextBox or Field

Hello I’m having trouble trying to find a way to add a Limit in a Text-box, Like under 12 Characters

something like this sorta

TextBox[‘String’] == Digits < 12

or so

It is called maxlen and is part of the property definition.

camera_name = bpy.props.StringProperty(name="Camera Name", description="Type an object name for the particle to orient towards. (i.e. TrackTo)", maxlen=12)

Read about it here:
http://www.blender.org/documentation/blender_python_api_2_68_release/bpy.props.html?highlight=stringproperty#bpy.props.StringProperty