You should be able to do this in either an Aggregate query and report or using a crosstab query; thus, no need for Excel... Unless you need the statistics, other financial tools, what-if analysis, or (like me) you have several people that are expecting an Excel workbook for the results and just will not change their ways.
Sum data by using a query (ACC2007) (I know this references Access 2007; however, on a fairly quick review, I didn't see anything in the article that wouldn't also be valid for ACC2003)
A few ways to get at the Access data:
You can link from Excel to Access:
[url=http://office.microsoft.com/en-us/access-help/import-export-and-link-data-between-access-and-excel-HP001095095.aspx]Import, export, and link data between Access and Excel[/ur] once you have the link established, then you can manipulate away.
Or you can take a look at the
TransferSpreadsheet Method (Access 2003 VBA Language Reference) A few things to note with this method is that it requires the use of a "stored" or "Named" query... that is to say, that you cannot use a SQL/Record-set at runtime. However, there are ways around this limitation using a parameter based query that pulls the data in question, I don't remember if ACC2003 will allow that or not for this method, or by adding/modifying a query in the QRYDEFS-Collection.
Then there is "Office Automation" where we can use a runtime SQL and then open a workbook and move the information from the record set into the workbook; however, this can be very heavy-duty VBA coding!