I agree with Pierce that the best way to do this would be to have different stages of the leads, and then trigger a notification to follow up with a specific lead only when it reaches a "qualified" stage. So while the sales rep would technically have access to the lead, the Stage should tip them off as to the urgency/relative temp of the lead. If you insist that for whatever reason sales shouldn't have ANY access or visibility to these early stage leads, you could assign them to someone else in your org - like the SFDC admin to start - and then whenever the lead becomes qualified you can reassign based on territory assignment rules dynamically - ie using a trigger vs batch sync. Make sense?
... View more