CAL et licenses for use of RDP server

Hello,

We have a SBS 2008 server, with 10 CAL, and 10 PC having their own MS Office license.

We are going to install in the same AD a W2008R2 server, used as RDP server.
The users will connect to this server in order to run a specific application and Word/Excel.

Questions :

1) We need RDS CAL, but do we need a CAL per physical user, or a CAL perconcurrent user on the server ?

2) What is the code of the RDS CAL to buy ?  Is it 6VC-02072 ?

3) Do we need extra MS-Office licenses (knowing that each PC already have one) ?
    Is yes, do we need a license per physical user, or a license perconcurrent user on the server ?

Thanks in advance for your help.