Hiding menu item from file right click drop down through REGISTRY

[matri06]

I have introduced a new drop down item "Encrypt" at right click to all file types - therefore I had to add it in the registry as:
HKEY_CLASSES_ROOT\*\shell\Encrypt
Now this drop down would be visible to all type of files at their right click.
But I also have files of type .crypt :

HKEY_CLASSES_ROOT\.crypt
HKEY_CLASSES_ROOT\encryptedfile (encryptedfile is defined of type .crypt)
Now I do not want this drop down Encrypt to be visible when I right click files of type .crypt (or encryptedfile)
For the rest of the files the menu Encrypt should be visible (enabled).
How can that be achieved?
I wish this functionality to be achieved by command line Registry modification, not by some third party tool or through C++,C# etc code
Thank you very much