running some function before view

Hi, 


I put notification bar on topbar. the data for notifications are set in MY_Controller.php
problem is:

For example there is notification where it says user has N unread messages. 
where N set in MY_Controller.
 
and then when user goes to unreaded message page, that notification should be decreased by 1, 
but as N set in MY_Controller and thus runs before Message Controller runs it will not be decreased by one.

What is the good way to solve this?

Thanks