Quickly Adding information in a new column

[buddah]

So There are two different styles of general ledger programs being used. I need to quickly and easily Reference numbers in a column and depending on what it is put another number in the last column.

So for example the xlsx file has these columns

ACCT NO | Description | Ammount
02-206300 Savings 400.00

And i need to add a 3-0-0-2310 So it looks like this

ACCT NO | Description | Amount | New Acct NO
02-206300 Savings 400.00 3-0-0-2310

There are 800 Different account numbers with new account numbers and multiple sheets that need to be processed with these numbers. I cant think of a way to quickly do this.



I have a key setup with the original number and the new number all together