Dougy,
I'm not sure that I have enough details to fully understand what you are trying to accomplish with your 5421, but it sounds like what you are looking for is a sequence of outputs from your Arbitrary Waveform Generator. This would be a program that would allow you to move from one arbitrary waveform to the next without reconfiguring your board between waveforms, which is what you appear to be looking for.
If this sounds like what you are looking for, then I would suggest looking at the example programs in LabVIEW's Example Finder. If you open up the Example Finder and browse to Hardware Input and Output » Modular Instruments » NI-FGEN » Arbitrary Waveform Generation, you will find examples called "Arb Sequence Example" and "Basic Arb Sequence Example." These examples demonstrate how to set up a sequence using standard waveforms (sine, cosine, ramp, etc.). To use these for an application like the one that you describe, you would need to make minor modifications to use your custom waveforms instead of the standard waveforms.
I hope that helps. Best of luck with your application.
Regards,
Jed R.
Applications Engineer
National Instruments