URGENT REQUEST: how to pull specific values from given query?

sourcetype=abc "responseStatus=500" "abc.xyz.logging.yyyy.zzzzz" "cccccccccccccc88888883333hhhh" | rex field=_raw "\"customerBilledAmount\" : (?.*?)," | rex field=_raw "\"resultID\" : (?.*?)," | rex field=_raw "\"customerID\" : (?.*?)," | dedup resultID | table userrBilledAmount resultID customerID Now I need to achieve - exclude all null - add up all userBilledAmount - exclude all null from userBilledAmount only