How Do I Reference Qualify Business Service based on Business Application

Hi Team,

I would really appreciate any help/guidance on how to achieve/modify the script I have, to achieve this.

On my Incident form I have a field for Service (business_service) and Business Application (u_business_application).

I want to put a Reference Qualifier on the Service (business_service) field, so that when Business Application is populated, the only options that show in the Service field are children of the parent Business Application.

I currently have the following script include and reference qualifier, which can be used to achieve the same, for showing CI's that relate to a service offering, but how can I amend this script include and the related reference qualifier javascript, so that I can achieve a similar process for only showing Service related to the Business Application.

Here is the Reference Qualifier Javascript I need to modify:

javascript: new IncidentUtils().getCis(current.service_offering);

And Here is associated script include I am wanting to modify:

var IncidentUtils = Class.create();
IncidentUtils.prototype = {

    getCis: function(so) {
        var getCiArr = [];
        if (so) {
            var cm = new GlideRecord('cmdb_ci');
            cm.addEncodedQuery('sys_class_name=service_offering');
            cm.addQuery('sys_id', so);
            cm.query();
            if (cm.next()) {
                var gr = new GlideRecord('cmdb_rel_ci');
                gr.addQuery('parent', cm.sys_id);
                gr.query();
                while (gr.next()) {
                    getCiArr.push(gr.child.sys_id.toString());
                }
                return "sys_idIN" + getCiArr.join(',');
            }
        }
    },

    type: 'IncidentUtils'
};

 Thanks very much - any help/guidance, very much appreciated.