function returning result set of varying column

Hi friends,
I am very new to plsql.

I have to write a function that quries few tables and returns a resultset
of varying column.

In that case I cannot predefine the table with column.
If I use RETURNS SETOF then I should know the number of columns and its
type?!

Is there anyway to return a resultset with any number of column?

Thanks for your help.

-maria