Working with time in a Rota Spreed Sheet

Hello,

I have a spreadsheet of a work rota, i have start and end time in seperate columns
, i need to work out how many hours each persons shift falls into a time range. ie if someone works from 12:00-22:00 and the range is 16:00-20:00 then this would be 4 hours, but if the shift was 12:00-18:00 this would be 2 hours of the range, if the shift was 19:00-22:00 this would be 1 hour....

Any Ideas??

Thanks