Exclude non-operational hours from a report

Hi there - I am looking for a way to remove non-operational hours from a report showing average response time per support group:

SELECT qd.queuename "Group",

convert(varchar(10), (avg(wo.respondedtime)-avg(wo.createdtime))/1000/3600)+':'+convert(varchar(10), ((avg(wo.respondedtime)-avg(wo.createdtime))/1000)%3600/60)+':'+convert(varchar(10),(((avg(wo.respondedtime)-avg(wo.createdtime)))/1000%60)) "Avg responseTime" FROM workorder wo

LEFT JOIN workorderstates wos ON wo.workorderid = wos.workorderid

LEFT JOIN statusdefinition sdf ON wos.statusid=sdf.statusid

LEFT JOIN WorkOrder_Queue woq ON wo.WORKORDERID=woq.WORKORDERID

LEFT JOIN QueueDefinition qd ON woq.QUEUEID=qd.QUEUEID

WHERE wo.respondedtime!='0'

AND wo.CREATEDTIME >= <from_thismonth>

AND wo.CREATEDTIME <= <to_thismonth>

GROUP BY qd.queuename