This is how I would do this.
First create a custom property for your interfaces, I'd call it Inactive, and make it a true/false (I chose inactive as opposed to active because t/f properties default to false) I'd probably make sure the description said something like "DO NOT TOUCH" because I don't want anyone messing with it by hand.
Then I'd create an interface alert with a condition of interface is down and has to stay that way for 14 days.
Resets automatically after 1 minute
The alert action would be to set a custom property, where it sets inactive to true.
The sets the stage for our second alert, this one triggers if interface status = up and interface Inactive = true, sends me an email that a previously inactive interface is now in use.
There are a couple ways you could tweak the logic if needed in your environment but that should be enough to get the ball rolling.