Align 2 columns and maintain association with 2 adjacent columns

I have 4 columns, the first two columns (A & B) are S/N and Start date. The last two columns (C & D) are S/N and Finish date. There is not necessarily a one-to-one relationship between start & finish dates.

I want to align the S/N's in columns A & C, and keep the Start & Finish dates associated with the S/N's. Then I want to add a fifth column (E) which calculates the Duration of the event (Finish date minus Start date). If there is not a match between S/N's (blanks), the Duration shall be zero.

Can this be accomplished using standard Excel functions?

Re: Align 2 columns and maintain association with 2 adjacent columns

I have two existing files that I need to merge. There are 7000 rows in one file and 6500 rows in the other file. That's why I need to first align the S/N's then calculate the Duration of the task. I cannot eliminate one set of S/N's, because there is not a one-to-one relationship. There may be unique S/N's in either file.