How do I select nth row from a table

hi ,

I have a table (USR_GROUP_TBL) with following attributes

grp_name char(30)
usr-name char(15)

In my C program ( with embedded SQL using ecpg)
I need to select the 'n'th user from the group.
Where n can any value from 1 to Max number of
users in the group.

The following query works well in non-embedded sql

select user_name
from mail_file_dtl
where grp_name = 'grp_1'
order by user_name limit 1 offset 5;

Will return the 5th user in the group 'grp_1'.

How can I incorporate this query in an embedded sql ??

I tried the following but ecpg returned error on the last
line.

exec sql
select mfl_size into :mfl_size
from mail_file_dtl
where mfl_recipient = :mfl_recipient
order by mfl_file_name limit 1 offset = :nNumber ;

Can a variable name be used in the offset option to pass
the value ?

I encountered a very similar problem when I tried to use
a cursor with 'move forward' option.

Thanks
ganesh