[Zope] How can I customize the propertysheet management interface?

Hi everybody. I have a ZClass with a propertysheet with a number of properties. I have created my own MyZClass_addForm and MyZClass_add in order to give users an interface to handle the creation of instances of MyZClass and the definition of the properties in the way I want them to do it. Now I would like to use a similar interface when the user needs to modify the properties, but I can not figure out how I can modify the .../propertysheets/my_propertysheet/manage page. I hope you can help me. Than you in advance. Regards. Fabio