My suggestion would be to not use repeating fields for this. There are other options you can use.
Could you elaborate on other options? This was strictly for reporting. As in categories down the left, months across the top and totals down the right and along the bottom. So would you say putting tabs between the months and output it on a giant textfield with set tab spacing?
This is called a 'crosstab' type of report. You have several other options that would seem easier to work with:
Create one ExecuteSQL calcualtion field for each column.
Use filtered portals for each column (a summary field in the filtered portal will show a summary value consistent with your filter expression)