Display an alert when clicked on a PREV or NEXT button

Hello everyone
I want to know how can i block the modification of the signed contract (with status: signed), when browsing the list using the Previous and Next buttons.

Thank u for help

You can do it via view.edit.php. Put your javascript to disable dropdown after display.


Thank u for ur replay
I dont want to disable dropdown after display, but i want to display an alert; that will block the change ,once I run into a contract ;whose status is signed during my journeyof list