How to access ritm variables (variables used in catalog item) using catalog client script?

I need to access the ritm variables in the catalog client script.

there is a field called "Select RITM" referencing sc_req_item in one of the catalog  item.

When a user selects an ritm from the above field, there should be an alert for "Billing rate" field value in that ritm selected.

Billing rate field is on the catalog item,its not on the ritm form.