In Excel 2003

I have two spreadsheets.  One with 1200 records, the second with 2600
records.

The sheet with 2600 records includes those records of the sheet with
1200, and shares a unique account number for each record.

I have been updating the 1200 record sheet, we have added numerous
additional columns, such as "status".

I need to take these new fields and created in the 1200 record sheet,
and match them to the unique account number and put them into the 2600
record sheet.

How can this be accomplished while keeping my sanity?

Thanks!