If they're run inside the BusinessObjects framework, then it can be logged by auditing. I'm assuming you're not the BO system admin, so you'll need to check with yours to determine whether auditing is turned on. If it's not, there is some configuration that will need to occur on the report server to get it up and running. If it is, then there are reports available in InfoView under a folder called Auditor which may show what you're looking for or there's a universe called "Activity" from which either a WebI or Crystal report can be created to get you that information.
-Dell
A computer only does what you actually told it to do - not what you thought you told it to do.