validate required fields before using custom email button

 

I have a custom button that I am using as a email button so we could have a cc address added. The code I'm using is:

 

form1.subform.Button3::click - (JavaScript, client)

 

var oDoc = event.target;
oDoc.mailDoc({
bUI: true,
cTo: "test@email.com",
cCc: "cc@email.com",
cSubject: "Title of the form",
});

 

Is there a way I can validate that 3 text fields are filled in before the button activates and opens the email?

 

Thank you for any help you can provide.