Hi Joe,
You can use the node status for this.
http://devcentral.f5.com/Default.aspx?tabid=53&forumid=32&tpage=1&view=topic&postid=812653812656
To set the node to disabled (Only persistent or active connections allowed), you can use 'b node 1.1.1.1 session disable/enable'.
You can use 'b node 1.1.1.1 down' to set 1.1.1.1 to forced offline (Only active connections allowed). You can reset the stats for a node by running 'b node 1.1.1.1 stats reset' and then check for active connections using 'b node 1.1.1.1 stats' and check the "cur" total.
Aaron