function shopper() {
    var isokay = 0;
    f = document.form;
    for(var i = 0; i < f.length; i++) {
        var e = f.elements[i];
        if ( e.name.substring(0,4) == "add_") {
          if ( e.value > 0 ) {
            isokay = 1;  
          }
        }
    }
    if (isokay == 1) {
      f.submit();
    } else {
      alert("Please enter the desired amount");
    }
}