[Zope-dev] ZClass Instances

Hi, I have a zclass, which have a propertysheet with some properties like multiple lines, strings, etc.. which have some default values that i assigned to them. When i create an instance of that zclass and i change the value of a property, then the instance does not reflect any more the changes that i make to the zclass, which is okey. So the question is: There is a way to know using an external method or with a dtml, if an instance is different from the zclass? Thanks.. Edgardo