Zend certified PHP/Magento developer

Cart page Total amount change observable

Three statements to explain my question:

Without page load:

  • I want to update one value on the same page via ajax request if cart
    total change.
  • I want to observe Cart Total changes by increasing/decreasing the
    quantity (by ajax) on cart or in mini cart or by removing the item
    etc.
  • On checkout_cart_index How I can call any js function if cart total
    change?