Complex validation

[eluser]bewhite[/eluser]
Hello!

I have small problem with validation of my form. I have to check if at least one field from the set contains data. I have looked at the user defined functions inside validation library but I still don't understand how can I create function that will process data from several field.

Does anybody know how to do this? Maybe I have to use another CI library or class in my case?

Thanks