Share an OUTBOUND IP address to the Internet - Content Filtering

Hi,

I'm looking to set up a Lab environment for students on Azure but I'm having difficult managing the Internet connectivity to prevent the use of dodgy sites.

I've been trying to use OpenDNS however the outbound IP address fluctuates as the machines are repowered.

Is there any way to ensure that all traffic is proxied via a single outbound IP?

Thanks