jQuery: Stop submitting form, perform script, continue submitting form?

$("#RequestCreateForm").submit(function (e) {
    if ($("#RequestCreateForm").validate().checkForm() === false) { 
       e.preventDefault(); 
       //form was NOT ok - optionally add some error script in here

       return false; //for old browsers 
    } else{
       //form was OK - you can add some pre-send script in here
    }

    //$(this).submit(); 
    //you don't have to submit manually if you didn't prevent the default event before
}

When you call $("#RequestCreateForm").submit(), the script will just run through the event handler again, and cause an infinite loop (as Koen pointed out in a comment on the accepted answer). So, you need to remove the event handler before submitting:

$("#RequestCreateForm").on('submit', function (e) {
    e.preventDefault();
    // do some stuff, and if it's okay:
    $(this).off('submit').submit();
});

The last line needs to be in a conditional statement, otherwise it'll just always happen, and negate your e.preventDefault(); at the top.

$("#RequestCreateForm").submit(function (e) {
    if ($("#RequestCreateForm").validate().checkForm() == false) 
    { 
         e.preventDefault();
         return false; 
    }        

    //other scripts

}