Script to close Pending Orders

I need a script that: close all pending orders when the magic number is not contained in Open Orders with that Magic Number.

If there is a Pending Order with "123" as Magic Number, and there is a Open Order with "123" as Magic Number then, that Pending Order is not closed. 

But,  If there is a Pending Order with "123" as Magic Number, and there is not an Open Order with "123" as Magic Number then, that Pending Order is closed.