Logistic Problem!

[ViolationCC]

Dear SMF Geniuses,

Well I have been planning to start my network of forums and this will basically involve 4 different forums under one company name. My problem lies the following:

I want the people who register to one of this forums to automically join the other 3 forums when they sign up in one of the forums. This means that members won't need to sign up more than once in any of m website.

How would I do that? Is there any mod that would do this for me?

~Kind Regards

Vio