Data source override in LBI

We are trying to create a datasource in LBI that will connect to a non-Lawson database that is on a server outside our network. We have been able to create a NAT'd IP for the server and connect to it with Crystal, but we get errors or a login prompt when we try to do it in LBI unless we change the Data Source to the Nat'd IP before it is published. The issue is the client does not have access to the server to change the Data Source themselves after publishing. They can't use the NAT when publishing because it won't resolve, so they have to use their internal IP. So how can this client publish reports with the internal IP, but have it pick up the NAT using Override Datasource?