CREATE OR REPLACE VIEW viewA
select col1, col2, col3 from tableA 
WHERE someDate BETWEEN START_DATE AND END_DATE

select col1, col2, col3 from tableA where '10-APR-07' BETWEEN START_DATE AND END_DATE

Setup:

-- global temp. table for storing the parameters
   CREATE GLOBAL TEMPORARY TABLE tbl_params (
      pname varchar2(255),
      psvalue varchar2(255)
   ) ON COMMIT DELETE ROWS;

   create or replace view v_test_paramview as
   (
      select * from mytable t
      where 
      -- if parameter is not set the view is executed unparameterized
      (t.myfield like nvl((select max(psvalue) from tbl_params p 
      where p.pname = 'v_test_paramview.pname' ), t.myfield))
   );

Test:

-- Just in order to show you that the param table is empty. 
-- Will be emptied by Oracle on commit, see definition of temp. table above.
select * from mfi_test_params;

-- set the parameter(s)
insert into tbl_params values ('v_test_paramview.pname', '<MY PATTERN>');

-- if the following select is executed before commit in the same 
-- transaction then the view parameter is being used
select * from v_test_paramview;

commit;

-- now empty again...
select * from tbl_test_params;