I have a Custom Skin Object which displays the summary of a shopping cart (number of items, value) as part of a skin layout.

I need custom modules on various shopping pages to fire an event that the Custom Skin Object can detect  which will allow it to refresh the cart summary when the cart is modified (new product added to cart, changes made in the View Cart for quantities or deletions, etc).  The prototype worked fine when the Custom Skin Object was just a normal module on the shopping pages using IMC and the OnModuleCommunication and IModuleListener interface.  Now that the prototype module has been moved into the skin as a Custom Skin Object, the IMC event no longer fires.  I gather that skins do not support the IMC interface. 

That said, then how can I establish a communication interface between a module on a page and a Custom Skin Object in a skin?

That won't work due to the code execution flow.  The skin object is near the top of the page and is processed and rendered before the click event is processed for the update cart/delete items from cart buttons. 

That's why you need to fire an event that the skin object can detect and re-render the cart summary once the cart has been modified in the button click event.