JQuery :: Unable To Stop Button's Code Behind?

Currently users select a record in a gridview and click on the delete button. Delete button passes certain variables to identify the record, makes a SQL connection and then deletes the record by executing a stored procedure. This is way the delete button's code behind works. Now we need a confirmation box if a certain flag is False. If the users select YES then they should be able to delete any way otherwise clicking on Cancel should stop the operation. I don't want to use the onClientClick event of the button like many examples on Web show, instead I am using the jQuery, that uses the button ID and pops up a confirmation dialog. The issue I am having is even if the Cancel button on the confirmation dialog is clicked it still goes on to run the code behind, executes the stored procedure and deletes the record. The browser being used is IE 7.0, how do I stop the button from running the code behind in the button_click event if they select cancel?

I have tried return false, e.preventDefault();event.propagation, event.returnValue = false etc but can't stop it. Here is the jQuery, that goes to the webservice when clicked and determines whether to display the confirmation or not when another stored procedure returns the record count of 0 or more. Like I said it works fine in getting the flag value from the SQL but does not stop at the client level and continues on to the code behind of btnDelete.

$(function() {
$("#btnDelete]").click(function(e) {
$.ajax({
type: "POST",
contentType: "application/json; charset=utf-8",
url: "WebServices/myServices.asmx/ConfirmDelete",
data: "{}",
dataType: "json",
error: function(req, msg, err) { alert(req, msg, err); },
success: function(msg) {
if (msg.d == 0 && !confirm("Do you wish to delete this record?")) {
event.preventDefault();
return false;
event.returnValue = false;
}
}
});
});
});