If you focus on a field and hold down the Control key (Command on a Mac) and press = it will bring up a message box that allows to do a bulk replace into the field in question.
You can either set the fields to the same static value, set them to a serial number or enter in a calculation if you need to enter in different values.
Is that what you are after?
Perfect - I was envisioning myself having to dig deep into scripts and calculations. It works and is exactly what I needed.