Return Offset Value from Lookup

Hello all, I have a task which I would like to excelerize
I have atached an excel workbook with a mini example of my task, but basically ,

you search column H for "X", when found you look at the row preceeding it in the same column H (row Y) - go to Row Y's Column B, grab that, bring it to column C of Row X and also program column D as =(C#-B#) WHERE # is the corresponding row of the Activesheet of column A, or B they both have the same size., basically calculating the duration here.. I do not know how to program a row to do that automatically, I do one and then holt ctrl + drag mouse down ..


thanks for reading and heres the file, its got a complete example, before and after,