So, if I understand you correctly, you're trying to update a set of reports by adding new formula fields. Is this correct?
You could look at the ReportAppServer SDK - the documentation is available at help.sap.com. There may be a way to use it without Crystal Server or BusinessObjects. I haven't really used it so I'm not sure.
Another way to handle this without actually typing the formulas in to every report would be to add them to one report, place the formula on the report, then copy the object and paste it into the reports where you want the formula. Pasting the formula object automatically creates the formula if it doesn't exist.
-Dell