Make a user Member of 2 Usergroups

[MigrosBudget]

Hey guys I got a question

Is it possible to make a User automaticly member of a second usergroup if he joins the first usergroup through the Usercp?

To clarify this I want to give a random example.

I got 3 usergroups in my forum:

• Registered Users (default)
• Customers (not joinable)
• Vip for lifetime (joinable)

The usergroup "Registered Users" is the default one, which you get when you register at the board. The "Customers" usergroup is just a tag which shows that you are a customer of our page, and then theres the "vip for lifetime" which indicates, that you paid some money or whatever.

Now what I want is, that when you join the usergroup "Vip for lifetime", then it automatically sets you also as a member of the "Customers" group, does anyone have an idea how to do that?

Thanks in advance