SQL & PL/SQL

Hi all
I've to take backup of a database weekly twice on every wednesday & Friday @ 5pm IST. I've written a hot backup script, which works every well.
now i want to automate the script. ie i want this script to run on wednesday & friday @ 5pm without any human interfearance ie with out actually any1 executing this script.
i created a batch file prod.bak with the following lines

@echo off
set oracle_sid=testdb
set oracle_home=d:\oracle\ora92
sqlplus /nolog
connect sys as sysdba/oracletest@testdb

this batch file when eexecuted connects me to sql prompt.

Now i want to execute my backup script bkp.sql automatically when it is connected to sql prompt.

(i tried with these lines in the above batch file...
call bkp.sql---it just opens the bkp.sql file in notepad & displays the script
start bkp.sql---same as call
connect / as sysdba/pwd@testdb@bkp.sql --- does not work simply remains a the sql prompt.
At 17:00 /Every:w,f "d:\bkp.sql"---does not work simply remains at the sql promt.)

Can any1 let me know what should i write in the batch file that will execute the bkp.sql file automatically after it gets connected to sql prompt. M using oracle 9i.
I'll manage he time through windows utility of scheduling task.. Let me know how to execute the .sql file from a batch file.

Thanks
Tripti