create another file associated with the script which will inject the parameter changing to the script.
modify the script so once opened to start first the "help1" file which will inject the parameter changing to the script, than to follow the script.
i can't help you for starting the script at an exact time
but how about at the end of the script write a line to leave an event to the machine, when the right time is reached the event will start.
i few words is this:
1.create the "injection file"
2.modify the script(first start help1 file, @ the end leave an event)
3.event___starts the script__>script___starts____the "injection file">injection file___changes the par.