need some help.

I am trying to add a custom field (checkbox) inside the Price Level record using form.addfield. I was able to display the checkbox it but it is not saving the value.
I also tried on afterSubmit and use setValue, however, I am not sure how to pass it on beforeLoad so I can set it on the .defaultValue, which only works on beforeLoad.
ANy possible workaround?

function beforeLoad(scriptContext) {
    let objPriceLevel = scriptContext.newRecord;
    let form = scriptContext.form;

    try {
            let fldSyncBox = form.addField({
                id: "custpage_syncbox",
                label: "Sync",
                type: serverWidget.FieldType.CHECKBOX,
              });        
              let bolPriceSync = objPriceLevel.getValue("custpage_syncbox");
              log.debug("bolPriceSync", bolPriceSync);

              fldSyncBox.defaultValue = bolPriceSync;
    } catch (err) {
      log.error("beforeLoad", err.message || err.name || JSON.stringify(err));
    }
  }