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The control protocol has a command called SetServiceAccount. This command takes two arguments, the Service Name and the Account Name.
SetServiceAccount <ServiceName> <AccountName>
For example: SetServiceAccount Pandora john@smith.com
To see how this command can make semi permanent changes, see the end of this article as it depends on the firmware version running on the MMS.
In order to do this programmatically, it may be necessary to retrieve a list of all service accounts available on the server. To do this, there is a command BrowseServiceAccounts that operates just like any other browse command where it takes a <start> and <count> argument. There is an additional, optional third argument where a specific service can be specified by name or GUID.
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As with all MMS control commands, it must be sent to port 5004 on the MMS. It must be followed by a carriage return and a line feed. Once sent, simply browse the service in question normally and the specified account will be preselected for you.
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