how to execute a stored procedure

I have created a procedure like this

PROCEDURE CALL_LOAD_ROUTINE(nu_file_control_number IN OUT NUMBER,
vc_csa_usr_id IN VARCHAR2,
vc_file_name IN VARCHAR2,
vc_file_desc IN VARCHAR2,
vc_load_typ VARCHAR2,
nu_sql_code OUT NUMBER,
vc_sql_errm OUT VARCHAR2)

I am trying to execute this procedure in sql*plus.
I have tried as
exec IBT_PKG_SML_LOAD.CALL_LOAD_ROUTINE(nu_file_control_number =>213,'admin','C:\System Testing Files\DatesTooTooMuch.xls','date fix test','SMLVALIDATION',nu_sql_code,vc_sql_errm)

But does not work.
I have declare the three variables before executing the procedure like
variable nu_sql_code NUMBER;
variable vc_sql_errm VARCHAR2;
variable nu_file_control_number NUMBER;
input nu_file_control_number=213;
then executed
exec IBT_PKG_SML_LOAD.CALL_LOAD_ROUTINE(nu_file_control_number,'admin','C:\System Testing Files\DatesTooTooMuch.xls','date fix test','SMLVALIDATION',nu_sql_code,vc_sql_errm);
this has given error as
ERROR at line 1:
ORA-06550: line 1, column 42:
PLS-00201: identifier 'NU_FILE_CONTROL_NUMBER' must be declared
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
.

Can anybody help , how to execute this procedure in SQL*PLUS.

Thanks in advace.

--Easwaran

U have to know something about order of parameters.
Try to make mapping ur call from formal to fact parameters and u
will undestend ur error.
Than : syntax of PL/SQL say to us:
We can't mix positioned parameters and named parameters in free order.
If we going to do that then:
-- First MUST be positioned parameters
-- Last MUST be named parameters