See the tabcmd synchgroups command here: http://onlinehelp.tableausoftware.com/current/server/en-us/help.htm#tabcmd_cmd.htm#tabcmd_Commands%3FTocPath%3DAdministrator%20Guide%7Ctabcmd%7Ctabcmd%20Commands%7C_____0
This should get at what you need.
I hope this helps,
Just a quick follow-up....
I did try this, w/o any "login" arguments in the syntax. Obviously, it gave me a " *** Cannot login because of missing arguments: --username,--server"
Is there a way to "encrypt" the file/script, specially if I were to put the userid/pwd in plain text? (Or is this a completely different topic?)