Controlling Navigation

Hi,

In our web pages there are different tabs available and there is a context panel which is common accross the pages.

At a time user can be in a particular tab, and this tab have form for user entry. we want to control navigation in such a way, that
if the user clicks on any other tab or context panel hyperlinks without saving changes(if he has added/modified any information) on the current tab, he should get an error dialog saying that he should save the information before moving out of the current tab.

Any suggestion how to do this?


Regards
Amit