Calling Master Page Method in Content Page

Hi All,

I am using nested master page , firstly there is a parent master and a second Master (ChildMaster) which inherits parent master .
In ChildMaster i am using treeview that is binded from database . This treeview is in update panel which update mode i have set as conditional.
Now from content page on button click event i am adding new value for treeview node , after adding value i ma calling childmaster method which populate treeview like this

((ChildMaster)Master).PopulateRootLevel();

while i am debugging cursor does'nt goes to this method.

what i have to do now ?