Can someone help with this?

I have a Spreadsheet called "ALL" which stores employee codes, ID's, Names, and additional details (One Row per employee)

My aim is to create the ability to 'bulk' insert into this sheet, with new data (new employees) but there needs to be a search condition which searches the sheet to make sure that the new data does not have any duplicates. If there are duplicates in Employee codes then only the other information is in the ROW is changed.

If I need to be more specific, please let me know.

Thanks
Daniel