how to pass values from iframe page to parent asp.net page.

I have a web page and and this contain three update panels.
 one update panel has a tree control, and other two panels has HTML tales.

Right now the tree control works very slow and also it behaves very abnormally some time.

so I am planning to remove the update panel1 and put the tree inside a new page and use Iframe to show that page.

Now this tree contains check boxes which user selects to view details on the other two update panels.

So i want to know how can i pass the nodes which nodes are checked to the parent page.
these nodes contains primary key as their values, so even if some how i am able to picks those values that will also be great

any one could help me how can i do this.