Overwrite existing record

Hi, I am a newbie...

I need to simply overwrite an existing record (row) in a dedicated workbook (db) with data copied from another workbook. The copied data has 234 fields with the first being a unique serial no.

I have code that currently pastes the record data into the next available row in the db workbook. This is fine until I need to update an existing record when I inevitably end up with a duplicate. Can someone please let me have the code that will find the existing record (if any) and overwrite it with the new data fields and if not existing paste in the next available row. It would be good if a message pops up before pasting warning the user that the record will be overwritten.

Your help would be greatly appreciated.

Why not use a database?