replace Footage file by script

in a project you can replace a footage file by pressing Ctrl+H when you select a footage. i want to replace a footage by the script. there is a command in javascript like "app.project.item(10).file.name" that return the file name of the footage, but it's readonly and i can't "app.project.item(10).file.name='test.avi' " so does anyone know how can i solve my problem?