Calculate time difference based on Status field

Dear Team,My requirement is to calculate the failure time, I just want to know the difference in hours where the status is 'I' and it shouldnt calculate if status is A [hr][b]StatusTime-- Status [/b]5/30/2016 12:30 A5/30/2016 13:02 A5/30/2016 14:02 I5/30/2016 15:02 I5/30/2016 19:17 A5/30/2016 20:25 A5/30/2016 22:02 I5/30/2016 23:30 IPlease help me