Thank you so much! I was able to get this to work, and now I can get a total for the years to show up correctly.
However, I still have what may be perhaps a less complicated issue pertaining to the same question. If I can get my Donations database to sort the way I want it to (i.e. find all the records for January 1999), can I essentially "select" these records in Donations (via a checkbox or whatever), and then have just these selected records appear over in Donors? If so, then can't I use a formula similar to your first solution to generate "one match" for each donor with a total, and then generate my letters based on that?
Maybe I made this sound too complex - all I want to do is have a certain selected set of records from Donations appear over in Donors. I can do all the sorting and finding in Donations, but I only want one record for each donor to "match" over in Donors, with their total. I want one record to show up in Donors, "Joe Blow", with whatever total applies to the 5 or 6 records I found for him over in Donations. That now works for one particular year, but it really needs to apply more to a date (>1/1/1999 for example). Does that make sense? Thanks again for your help!!