Make catalog variables editable for a particular group memebers

Hi All,

I have a requirement to make the RITM variables editable for a particular group members once the RITM is in 1st stage of approval.

for example: 1st stage of approval goes to 'Business Solution' group, so the members of that group should have access to edit the variables on the RITM form.

I have written a client callable script include to check the group membership. If it return true, variables should be editable over RITM form but the variables are not editable. 

Script Include:

var canEditRITMVariables = Class.create();

canEditRITMVariables.prototype = Object.extendsObject(AbstractAjaxProcessor, {

    // Client-callable function

    canEditRITMVariables: function() {

        var userSysId = this.getParameter('sysparm_user');

        var groupSysId = this.getParameter('sysparm_group');

        if (this.isUserInGroup(userSysId, groupSysId)) {

            return 'true'; // user can edit

        }

        return 'false'; // restrict editing

    },

    // Helper: check group membership

    isUserInGroup: function(userSysId, groupSysId) {

        var grMember = new GlideRecord('sys_user_grmember');

        grMember.addQuery('user', userSysId);

        grMember.addQuery('group', groupSysId);

        grMember.query();

        return grMember.hasNext();

    },

    type: 'canEditRITMVariables'

});

Client Script:

function onLoad() {

    //Type appropriate comment here, and begin script below

    if (g_form.getValue("cat_item") == "d025b6ff870ce950fa770d47cebb3566") {

        var ga = new GlideAjax('canEditRITMVariables');

        ga.addParam('sysparm_name', 'canEditRITMVariables');

        ga.addParam('sysparm_user', g_user.userID);

        ga.addParam('sysparm_group', '56f1f8240f9d82004fb50f8ce1050e2f'); // replace with group sys_id 56f1f8240f9d82004fb50f8ce1050e2f

        ga.getXMLAnswer(function(response) {

            var canEdit = response === 'true';

            if (!canEdit) {

                g_form.setVariablesReadOnly(false);

            }

        });

    }

}

Can someone plz help on this why this code is not working. I have ran the code in the scripts-background and the result is coming as true still the variables are non-editable for the users.

Thansk,