GridView-set a flag when the page/row data is change

Question

GridView in vb.net - no Ajax,jQuery

Scenario:
 When a user clicks on Edit Command Link Button, it navigates the user to Update/Cancel the Row Data

Need a Trap To -

• disable all other Edit/Delete command link button on grid rows
• set a flag when the page data is changed for the current row in update mode and
• check it if the user tries to navigate away before clicking update, force him to either click update/Cancel

Solution: any examples in vb.net/C#

Thanks for your knowledge sharing