Dynamic Query for System functions - now()

Dear Friends,

I am using PostgreSQL 7.3.4 Server on RH Linux 7.2. I am trying to generate a dynamic query to fetch the next month interval.

select now()+ interval'1 month'; -- This is working fine.

I wanna dynamically assign the interval number. i,e --> select now()+ interval'n month';

For this I wanted to write a dynamic query.
EXECUTE 'select now()+ interval\'' || 3|| 'month\'';
Error
ERROR: parser: parse error at or near "'select now()+ interval\''" at character 9

Help help me with this. I wanted to use this query inside a PLpgSQL function.

Regards
Kumar