plpgsql function Syntax

Is it possible to get a select statement to work like this with a for loop?

CREATE FUNCTION public.search(int4)
  RETURNS SETOF search1 AS
'
DECLARE
category alias for $1;
newrows search1%rowtype;
rec RECORD;
SQLCommand varchar;

BEGIN
    IF (category = 0) THEN
        SQLCommand := 'SELECT * FROM table';
    ELSE
        SQLCommand := 'SELECT idnumber FROM table';
    END IF;

    FOR rec IN SQLCommand
        LOOP
            ...blah...
            ...blah...
    END LOOP;

Basically I want to create the SELECT statement dynamically and then use
that select statement in subsequent querries later in the function.  Will
this syntax work or should I try to use a VIEW?

Thanks,
Derrick