Hmmm....
Not what I am used to but that is the fun...
Does the userID appear as a parameter in the report, or is it passed to a stored proc and the results of the stored proc displayed?
If the userID is available prior to the report being run, you can probably use it select the data that you want using a command object.
Again, it is not something that I have needed to do, and others have reported that CR may request a value for the parameter before the report will get very far(because of the command object) but this would seem to be good case for the command object.
HTH