[wix-users] How can I control what an added Change button in my bootstrapper’s Modify Setup does?

[Linda Barnhart]

Using WiX toolset version 3.10 in Visual Studio 2019.

I have a setup with a custom UI. I have a bundle/bootstrapper as we have a
prerequisite to install if needed, and an exe was the required output of
the VS build.

After installing, in ARP which displays the setup’s UI, the Change button
calls a custom MaintenanceWelcomeDlg whose Next button calls a custom
MaintenanceTypeDlg which has an Update button that calls a custom dialog
that prompts for and validates a registration key (as the setup does on
install when needed). Works great!

I’d like the added Change button in the bootstrapper’s Modify Setup to work
the same as it does in ARP. I can add a Change button to display on the
boostrapper’s Modify Setup dialog BUT cannot find how to Control what it
does. What am I missing?

Thanks for any and all suggestions and/or links to help me with this.