How to update display hook ?

[Jibax]

HI there, I want to know how to update a value return by a display hook. 

For example, when a customer is modifying the content of the cart, the actionCartSave hook is executed, and I would like to update a text on the same page ( the text is returned by displayProductPriceBlock for instance ). 

But when I called

Hook::exec("displayProductPriceBlock", array())

at the end of hookActionCartSave() method, the function hookDisplayProductPriceBlock() should be executed and return updated data. But nothing happen. 

Is this a correct behavior ? If no, how to manage to update displayed value return by a display hook without refreshing a page ?