Dual Level Ad Management in MultiSites

Greetings. I am looking at all of the ways in which ads can be inserted into sites.

Using Multi-Site, is there a way to have network wide ads managed by the network admin, while the individual site owner has the ability to run their own site specific ads in conjunction with my network ads? Can this be done with any existing plugins?

I hope I have explained this sufficiently. Basically a two-tiered system.

TYVM. - Frank