Debra Dalgleish shows techniques to reset that last used cell:
http://contextures.com/xlfaqApp.html#Unused

Jessica G wrote:

I have an Excel file that I convert into a CSV file. The information in this
file is usually no more than 400 records. If I view the CSV file in Notepad,
sometimes the file contains 65,000+ records, which has my 400 records and
empty lines that contain commas only. But sometimes it only contains my 400
records. I need to figure out how to eliminate the extra records because I
have to import this into my payroll software.

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Dave Peterson