// custom-module.js
define([], function () {
  function printInvoice(invoiceId, templateId) {
    // print logic
  }

  return {
    printInvoice: printInvoice
  };
});

// user-event.js
define(["./custom-module"], function (myModule) {
  function afterSubmit(context) {
    var invoiceId = context.newRecord.id;
    var templateId = /* however you retrieve it */;
    myModule.printInvoice(invoiceId, templateId);
  }
  // rest of UE
});