Is there a way to dynamically choose a report instance for BI Web Services?

Hello,

BI Web Services is extremely promising and the only thing I can't figure out right now is if we can dynamically select which report instance to use. We can do refresh on demand or choose the latest instance, but other than that I'm not sure what else is available.

It would be great if we could do so, that way we don't need to maintain a historical table if we wanted to get previous snapshots in time.

Any comments would be appreciated.

Thanks!

David