One way to do this would be to create a third 'wrapper' setup for both the original setup & the patch in the Editor. This 'wrapper' setup would install nothing, but would call two custom actions in its sequence. The first custom action would launch the original installation silently. The second custom action would launch the patch silently. Launching them silently ensures your user only has to deal with one UI(the wrapper). This would serve your purpose at the sacrifice of a small size increase in what you're distributing due to the wrapper setup.
You could also repackage them both into a single setup as you mentioned, but depending upon how complicated the original setup is, my first method may prove a little less time consuming if your only purpose is to launch both setups as one setup.
You can find help on creating custom actions in your AdminStudio help library.
Hope this helps.
Mark Doeseckle
Software Quality Engineer
InstallShield Products, Macrovision Corp.
