Form validation callback, pass input name?

[eluser]tomclowes[/eluser]
In many of my forms, I need to check if the users input is unique. I.E There is no row with that same value in my database.

For example when a user types in a username, i want to check it is unique using a form validation callback.

I want to extend this, so one function can be used to check whether ANY form input is unique.

The idea is that the name of the input is "dbname_fieldname".

Is there anyway in a formvalidation callback to pass the field name, as well as the user inputted value to the callback?

THANKS