Preferred Wifi Network Order

Is there any way to order known wifi networks, so that the iPhone will connect to a specific network when it is available, regardless of what other networks are visible?

I have a wireless router set up in my office. My office network is faster and more reliable than the campus network. However, the SSID of the campus network is broadcast in a much larger radius. This results in the following situation: In my office, I connect to my office network. As I leave the campus, my iPhone loses the signal for my office network and automatically connects to the campus network. When I return the next day, my iPhone automatically connects to the campus network, the last known network to which it was connected. However, as I approach my office, the iPhone will not automatically connect to my office network, since it is already connected to the campus network. Consequently, in order to get the better connection, I have to manually connect to my office network whenever I return.

I would like to configure my iPhone to automatically connect to my office network when available, despite the fact that it may already be connected to the campus network. Is this possible, or must I manually set the network every time I return to my office?