What you've got there isn't really an uninstall dialog, it's a maintenance
dialog because you're attempting to install the exact same product twice,
and that doesn't make much sense, so it says either repair it or uninstall
it. An uninstall can call a custom action, you can just add them in the
Visual Studio IDE and condition them on something if you like. An uninstall
from Add/Remove Programsd won't show that maintenance dialog - it will just
remove the product, so a button on that maintenance dialog isn't much use.