BYOD. Using 3G over WiFi for some apps

Hello,

I was told this can work but I don't see any way to do it. So I will post it here. There are 5 people on this company with an iPhone. There are access policies in the WiFi usage (I am in charge of those policies). As an example of my policies: Facebook: allowed Youtube: blocked.

So, these 5 people are using some apps within the enterprise, so they do need to be connected to the WiFi network beacause the info for those apps (enterprise apps) are in some servers inside the network. But, when they are connected to the WiFi network can't access to Youtube, so they get disconnected. I asked a lot, and some iPhone gurus told me that: There is a way to make your iPhone request some internet applications over 3G when WiFi doesn't allow it.

Is there a way to do this?

Thanks in advanced.

Miguel