Three button alert

I have an alert window that requests information before extracting certain fields from a form and putting their data into an email. I want the Cancel button to simply close the alert without generating the email.

The alert code looks like this:
var oDlg = app.alert({
cMsg: "Is the device OK to place?",
cTitle: "Placement Verification",
nIcon: 2, nType: 3
});
if ( oDlg == 4 ) var cOkay="OK";
if ( oDlg == 3 ) var cOkay="NOT OK";

I would hope that there would be an easy way to set oDlg == 2 to do nothing. As it is, the Cancel button sets cOkay to "OK" and produces the email.

My suspicion is that I need to wrap my entire code in a function or something so that I can escape the window. I've tried such a scheme adding a "break;" but I always get an "invalid break" error no matter what I do.