I would like to know if it is possible for me to have my clients update from the web when they are off site and update from the master repository when they are onsite. If so can yuou please point me in the right direction.
I don't believe McAfee has a website that machines can go to when not on internal network.
VSE updates are based on a product update task, in which the agent will try and pull VSE updates based on repositories you have listed in the McAfee Agent > Repository policy. Have you looked at the "Proxy" tab of the agent policy and tried setting up a proxy in which the agents can get through when not internal? That might help you out.
VSE update usually give first priority to ePO server then to the McAfee ftp server.
This also depends on the policies which you set in the repository policies of McAfee Agent.
This will be possible, where mcafee http repository must be enbled for clients from mcafee agent repository policies in ePO.
check for the policies of repository, if you enabled mcafee http it will take updates from mcafee site on public network where master repository not avilable.