Can I designate a wireless network that always takes precedence, if available?

I suspect there may not be a way to do this, but I thought I'd check with the experts. Here's the situation:

There is a wireless network at my work (Work), and at my home (Home). However, I do some work from home, and so I have an Aruba wireless box that means the Work network is also available in my house in order to give me access to my employer's VPN.

When I'm at work during the day, I use the network Work on my iPhone. When I come home, it will always automatically connect to my VPN enabled Work network at home, rather than my Home network. And I have to remember to switch it manually.

I've tried forgetting both networks, and re-adding them in the order Home, Work, but that hasn't helped. I suspect the phone is simply connecting to the network it saw most recently.

I realize this isn't the biggest problem in the world, as I can always change it manually. But is there a way to have the phone always connect to a designated network when it's available?

You are right. There is no way of setting preferred networks on iPhone's iOS 5.