To show "treat entered string text" to null & empty?

It's regarding the better representation of showing these option. I would like to explain in an elaborative way.

"A user can set data modification setting for further use. which might help other member users."

User might set few Execution Options:

1. Treat empty text as null.
2. Treat ______ text as null.

Treat text ___________ as null string (checkbox) Treat text ___________ as empty string (checkbox)

Note :_______ is entered value of user

I have tried few but not working for users