Try this,

=(NETWORKDAYS(A1,B1, luHolidays)-1)*(luDayEnd-luDayStart)+IF(NETWORKDAYS(B1,B1,luHolidays),MEDIAN(MOD(B1,1),luDayEnd, luDayStart), luDayEnd)-MEDIAN(NETWORKDAYS(A1,A1, luHolidays)*MOD(A1,1), luDayEnd, luDayStart)

format result cell as [h]:mm