I know this is an old post, but for others that stumble upon this answer as I did, there is a way to prevent new submissions from the onSubmit function. In your onSubmit function, do a check for the exposed request status:
onSubmitFunc : function() {
if (_.request.status == -1)
{
alert("Sorry, new submissions are not allowed at this time");
return false;
}
return true;
}
Any previously submitted requests will have their request ID populated in that variable instead. Make sure at the end of your function you return true as it appears the system is looking for confirmation that a submit is good to go.