Working Hours in a Working Week Calculation

Hi Folks,

Hopefully this is just a quick one please:
I have a cell with a field showing the following in a DD:HH:MM format - 27:04:07. Therefore this is 27 days 4 hour and 7 minutes. What I require is for another cell to convert this in to a working week - 5 days a week at 8 hours a day. So 27 days could well only be 05:15:26. I am not sure if 05 days is the right answer - just racking my brain and going in circles. What I currently have is: =A1/24*((INT(A1/"8:00")+((MOD(A1/"8:00",1)/24*8)))/7*5)

Thanks for any help

Andrew