=(NETWORKDAYS(date1+1,date2-1,holidays))*9
+((WEEKDAY(date1,2)<6)*(NOT(ISNUMBER(MATCH(INT(date1),holidays,0))))*(MIN(MAX(0,--"18:00"-MOD(date1,1)),--"09:00"))*24)
+((WEEKDAY(date2,2)<6)*(NOT(ISNUMBER(MATCH(INT(date2),holidays,0))))*(MIN(MAX(MOD(date2,1)-"09:00",0),--"09:00"))*24)