High Importance Email Javascript?

I have a form that can be submitted as a Rush request or a Regular request. I have already written my script to include Rush or Regular in the email subject line. I would like to know if there is a way I can automatically make the email (Outlook) High Importance when the Rush timeline is selected? I am also not sure if this code would be added to the email code or to the Timeline field for Rush?

This is what my email code looks like:

// Set the subject and body text for the email message

var cSubLine = this.getField("Timeline") + " " + "Request Form";

var cBody = "Thank you for submitting your form.\n"

Thanks!