declare bind variables in script - sql

Question

I have script that uses this variables
with
TIME_DATA as ( select $$D:=:DA$$ td from dual),
GROUP_INFO as (select $$N:=:GR_ID$$ gr_id_number from dual),
and uses them like this
A_PLUS_TEK as(select point_id, ml_id, ml_name, val a_plus_month, DA
from VALUE_DATA, TIME_DATA
where ml_id = 381 and DA = trunc(td, 'MM'))
I want to know how to initialize this variables, now when I run script I have this ouput:
Bind Variable "DA$$" is NOT DECLARED
EDIT: Usually users enter this values on website, I have access only to database, where I got script from reports table. Also I want to know how to initialize this variables from c#.
EIDT2: I took this for example (How do I use variables in Oracle SQL Developer?). It works.
variable v_count number;
variable v_emp_id number;
exec :v_emp_id := 1234;
exec select count(1) into :v_count from emp;
select *
from emp
where empno = :v_emp_id
exec print :v_count;
my code:
declare
variable DA$$ VARCHAR2(80);
variable gr_id$$ number;
begin
exec :DA$$ := to_date('2011-09-13 09:00:00', 'YYYY-MM-DD HH24:MI:SS');
exec :gr_id$$ := '1341';
BEGIN
and then with statement :
WITH
TIME_DATA as ( select $$D:=:DA$$ td from dual),
GROUP_INFO as (select $$N:=:GR_ID$$ gr_id_number from dual),
....
END;
But still have this
Bind Variable "DA$$" is NOT DECLARED
anonymous block completed
This also change nothing
exec :DA$$ := '2011-09-13 09:00:00';
I think that DA$$ is date, because it used in trunc() DA = trunc(td, 'MM'))
When I select Run Statement(trl+Enter), Sql Developer offers to enter bind variables, but I don't know how to enter date.
EDIT3: Finally I do this without Declare, Begin, End and it works :
variable DA$$ VARCHAR2(80);
variable gr_id$$ number;
exec :DA$$ := to_date('2011-09-13 09:00:00', 'YYYY-MM-DD HH24:MI:SS');
exec DBMS_OUTPUT.PUT_LINE(:DA$$);
exec :gr_id$$ := '1341';
with
TIME_DATA as ( select $$D:=DA$$; td from dual),
GROUP_INFO as (select $$N:=:GR_ID$$ gr_id_number from dual),
...

Answer 1

From C# you can do this:
// using Oracle.DataAccess.Client
using(OracleCommand command = new OracleCommand(commandText, dbConnection))
{
command.CommandType = CommandType.Text;
command.Parameters.Add("DA$$", OracleDbType.Int32, valueDA, ParameterDirection.Input);
command.Parameters.Add("GR_ID$$", OracleDbType.Int32, valueGR_ID, ParameterDirection.Input);
}
But review your comand text. Because you will probably face syntax errors due to "$$D:" and "$$N:"