Kevin,
I had posted on this a while ago. There is a built in service which can change the adapter connection for an adapter service but is not recommended to be used in Runtime, rather at design time.
One way, I have done this is to have multiple adapter connections setup first. Then create a flow service which invokes an adapter service dynamically based on input (there are several ways to do this as well).
Thanks.
Eric
#webMethods#Flow-and-Java-services#Integration-Server-and-ESB