SQL & PL/SQL :: Want To Define Dynamic Type For A Variable In Oracle 10g

I m trying to give table name as parameter to this function. It is compiling properly.But when an anonymous block is created to call this table value, it has to be fetched into a variable of Rowtype of this inputted table. So I am not able to create any ROWTYPE variable for this table dynamically.

//Function
create or replace function instant_tabula(tabula in varchar) return sys_refcursor
as
cur sys_refcursor;
str varchar2(20000);
begin
str := 'select * from ' || tabula;
open cur for str;
return cur;
end;
[code]....