Auto-populate date in last cell when other cells in the row are changed

I’m using Excel 2000. I have a worksheet with multiple rows of data where each row represents a project and information related to that project. The last cell in each row is a “Last Updated” field, intended to capture the date that the last changes were made to cells in that row. It would be nice if those “Last Updated” cells would auto-populate as appropriate whenever the file is saved. Does anybody know how to do this?