// -------------------------------------------------------------------
// TabNext()
// Function to auto-tab serial field
// Arguments:
//   obj :  The input object (this)
//   event: Either 'up' or 'down' depending on the keypress event
//   len  : Max length of field - tab when input reaches this length
//   next_field: input object to get focus after this one
// -------------------------------------------------------------------
var serial_field_length=0;
function TabNext(obj, event, len, next_field) {
	if (event == "down") {
		serial_field_length = obj.value.length;
	}
	else if (event == "up") {
		if (obj.value.length != serial_field_length) {
			serial_field_length = obj.value.length;
			if (serial_field_length == len) {
				next_field.focus();
			}
		}
	}
}