Use Javascript to set Embedded Data with addOnUnload

I want to use "Qualtrics.SurveyEngine.addOnUnload" to set embedded data with Javascript. I want to use "addOnUnload," though, so I can compare 2 values from questions in this block. Here is my script. The console.log returns the values I expect to see, but the embedded data is not set.
Note: In my survey flow, I have a "Set Embedded Data" block with the defined data before the block containing this script. I tried putting it after the block. That didn't help.
//set zip code data
var zipArray = [
"84003",
"84004",
"84005",
"84116"
]
var var1 = jQuery("#QID10").find(".InputText").val();
var placeholder = jQuery.inArray( var1, zipArray );
var saltLakeZip = ''; // extra step but helps with console.log troubleshooting.

if (placeholder != -1) {
saltLakeZip = 'yep'; 
Qualtrics.SurveyEngine.setEmbeddedData( 'saltLakeCityZip', saltLakeZip ); //Qualtrics embedded data

} else {
saltLakeZip = 'nope';
Qualtrics.SurveyEngine.setEmbeddedData( 'saltLakeCityZip', saltLakeZip ); //Qualtrics embedded data
}
console.log('saltLakeZip = ' + saltLakeZip)

//set ticket data
var var2 = jQuery("#QID18").find(".InputText").val();
var theID = '';

if (var2.indexOf("Salt Lake City") !== -1 && saltLakeZip == 'yep') {
theID = 'SLC';
} else {
theID = 'AAA'
}

Qualtrics.SurveyEngine.setEmbeddedData( 'ticketID', theID ); //Qualtrics embedded data
console.log('ticket01 = ' + theID);

//console.log returns the correct values, but qualtics won't set teh embedded data.


If I use "Qualtrics.SurveyEngine.addOnload" with a blur on each question field, then the Javascript will set the embedded data, but that doesn't work for me because I want to compare the two values AFTER the user is done making changes and clicks the "Next" button.