Hi,
No, there is no built-in way to assign ip addresses by user. There is a RD ip virtualization feature in Server 2008 R2 that allows different ip addresses to be assigned to each session or each program. The addresses are assigned via
DHCP or via a manually-configured pool of addresses in the server's registry. Again, the addresses are not assigned to specific users--they are automatically assigned as sessions are created or programs are run.
http://technet.microsoft.com/en-us/library/dd759263.aspx
-TP