select refcursor into a variable

Hi all,
   I'm executing dynamic queries in postgres7.2.3. Is there a way I can
execute a refcursor and then select it into a variable and then return that
variable? My query returns the sum of values. So its only one single
value...that I want to select into a variable. How do I do this. 'cos I
don't wnat to return a refcursor.

Thanx
Madhavi