using Oracle 9i
I am trying to create a report that will look at a user variable
and append sql criteria onto the end of the sql statement based
on the variable.
Example:

define x = '&1'

If &x = 'A' Then I would like to append 'WHERE test_column > 5' to the end of the statement.
If &x = 'B' Then append 'WHERE test_column > 500' to the end.
and so forth.

I am able to get the results through PL/SQL below but I am not sure how to pass that variable to sqlplus.
DECLARE x varchar(25) := 'A';
y varchar(30);
BEGIN
SELECT DECODE(x,
'A', 'WHERE test_column > 5',
'B', 'WHERE test_column > 500',
'C', 'WHERE test_column < 5')
INTO y
FROM DUAL;
select disc_Cd from disc y;
END;
/
select disc_Cd from disc y