Comparing spreadsheets

I have two huge spreadsheets (64,000 rows +)  I stripped out key fields and saved to text files.  I then used WinMerge to find the differences.  There are 2,000+ rows that are in one and not in the other.  I now want to identify those rows (the complete row) in the original spreadsheet so I can import the data into an Oracle database.  Haven't figured out how to extract just the rows that are in the difference file (that just has 2 key fields).   Any help would be appreciated.