Throttle bandwidth for subnet for a specific period of time

How do I cap bandwidth for a specific subnet for a specific period of time? I want/need to cap a subnet to xx M/b between 8:00 and 4:00 on Wednesdays. Otherwise, the subnet can be at regular usage.

This is mix/cross between a policy and traffic shaper. I'm using OS 5.4.10. 

If this is possible (or easier to do) in 5.6.x, or 6.0.x, I'd be willing to looking into updating.

Thanks.