adressing column

i have the following function:

declare
 prim_col_name Alias for $1;
 prim_col_val Alias for $2;
 my_column Alias for $3;
 link_table Alias for $4;
 link_col Alias for $5;
 data_table alias for $6;
 my_record Record;
 result_string varchar;
 i integer;
begin
 result_string := '';
 i := 0;
 For my_record in execute 'select ' || my_column || ' from ' || 
data_table || ' where ' || link_col || ' in (select ' || link_col || ' 
from ' || link_table || ' where ' || prim_col_name || ' = ' || 
prim_col_val || ') order by lower(' || my_column || ')' loop
     if i = 0 then
        result_string := my_record.col;
     else
        result_string := result_string || ', ' || my_record.col;
     end if;
     i := i + 1;
 end loop;
 return result_string;
end


now i am searching for a way, to access my_column in my_record (now it 
just works if  my_column = 'col')
can anyone help please!
thanx
steffn