how to reference the inactive field on a customer record via SuiteScript?

I am trying to check if the inactive field on a customer required has been ticked or not. If its been ticked, then I want a message to appear.

I am using a client script to do this and have this working fine on custom check box fields on the fieldchanged function, but for some reason I cannot get this to work on the isinactive field on the customer record.

My code:

 define(['N/record','N/ui/dialog','N/format','N/email'],

    function (record,dialog,format,email) {

        function pageInit(context){}

        function fieldChanged(context) {

            //Set variable to current record

            var currentRecord = context.currentRecord;