Email depending on value in registration form

I have built a user registration system using SecurityAssist which requires admin approval before the user can access the site. Everything's working great, but I have two admin people, one who gets emails letting them know when anyone registers, and the other who should only get an email if the "Member_Type" dropdown selection in the registration form is a specific value. I have two Universal Email behaviors set up, one for each Admin person, but currently the trigger is "any form post", so both admins get all registration emails. I see I can use a dynamic value but I'm not sure how to construct it. Basically I only want to send an email to the second admin person if the Membership_Type dropdown field in the form's value is "3", so would this be the correct syntax?

((isset($_POST["Membership_Type"]))?$_POST["Membership_Type"]:"3")

Thanks
Margaret