Notification Dynamics 365

Hi, 

I am trying to set up a field based notification on a contact form.

e.g. I have a field named Membership, which is option set with three options. I would like a notification when i choose one of the options.

I have tried the below code but it shows a notification regardless of the option i choose. 

function setMembershipNotification() {  
    var membership = Xrm.Page.getAttribute("spl_membership").getValue();  

    if (!membership) {
Xrm.Page.ui.setFormNotification("You are a Executive Memeber", "INFO", "928,350,002");
} 
else {
Xrm.Page.ui.clearFormNotification('928,350,002');
}
}

Any suggestions on how i might be able to do this.

Thanks

Damesh