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Hi. I am an entertainment attorney and can help you with this.
You would approach this through contract negotiations. Your agreement would have to assign the purchaser the copyright in the script but explicitly exclude all derivative rights (i.e. all rights to take elements of the initial copyright and create new works based on that copyright).
You cannot trademark a name.
Unless that name is XXXXX XXXXX the branding of a specific product and has been used in commerce (think McDonalds).
Please let me know if that answers your question.