|What you are asking for can be done with a macro.|
Code could be written to search for Accounting Numbers and then create tabs/copy the data for each account.
In order for us to offer specific code, we would need something more than "The file looks something like this..."
We would need some more specifics as to where the Accounting Numbers can be found (e.g. every 6th row or randomly strewn throughout the file or one row above SSN, etc.).
We would also need to know what needs to be copied and how we can identify that (e.g. one row above the Accounting Number and 2 rows below or one above and keep copying until a blank row is found, etc.)
Is it as simple as just copy everything between each blank row with the Accounting Number always being the second entry in the group?
BTW...does thousands of rows mean thousands of Accounting Numbers and therefore thousands of tabs?