Changing the template (skin) for few users ?

[Suri.CMS]

Hi All,
I have 2 templates (skins).

I have set the Skin # 1 by default to all users and they can't change it (Users can change skins = NO).

Now I want to assign the Skin # 2 to some users (3 or 4 selected users only).

What value & Where should I change for that in my DATABASE table ?

Note: I have set styleid=2 (This is Skin # 2) for one user.
Then I went to my home page, logged in as that user and refreshed it.
It did not show the changed style. It still shows the default one.

I don't know where else to change it.