Restrict access to MY EA

I have a number of EA's that I would like to restrict access to individual MT4 Terminals

I have the MQ4 files thus can edit the code of the EA

Scenario 

Someone wants a copy of my EA

Before I give it to them I ask for their MT4 Account No

I enter the code to my MQ4 file (that you will provide)

I create an ex4 file 

Send the ex4 file to the person 

My EA will only work on that specific terminal and no others

Job complete

Job is marked as complete when the developer

Provides me with a code I can use to lock down my EA

The only thing I'll need to do moving forward is enter the MT4 number of the account that can access my EA

I should be able to copy this code onto all my EA's and restrict access