AFAIK, there is no way to do this directly in BO. You would have to use a viewer and write code that would do the following:
1. Get the report and load it into a Report object.
2. Set the LogonInfo for each table in the report. Stored Procedures are seen as a "table" for this situation.
3. Open the updated Report object in a viewer.
Code could be written using the .NET SDK in Visual Studio 2010 or 2012 or using the Java SDK.
If your report were connecting through a universe, there would be a fairly easy way to do this in BO using Universe Overloads. However, I've never been able to get a stored procedure universe working.
-Dell
