Prevent change link in textarea "Share a link with your followers"



I’m building some webpage and there I’d like to have profit system such like “share us on twitter and receive some benefits”. I’ve almost done it but is one problem. After when user click on link he have textarea “Share a link with your followers” and there he’s possible to change link to share (possible to change even on some different website) . Is possible to prevent change text(link) share in this textarea?