[Samba] Force GID specific number

[Nir B]

Hi All,

My linux machines are part of NIS domain, I want to move them to work with 
my AD using winbind.
The clearcase permissions are based on specific GID (50).
I saw that you define on the smb.conf  "idmap gid = 10000-20000" and all 
your AD gruops GID start at 10000
Is there any way to force that each user will get GID 50 as one of his 
groups?

Thanks In Advanced!

Nir B