Forcing Wix to go do a download page for a required component

When I build an MSI in Visual Studio, I have the option of specifying required components (in this case, MSXML6), and if the component isn't installed then the installer would say that it was needed, and would open a browser to the download site for the component.

How can I implement this using Wix?

(Note that I don't necessarily want it to install the component, just exit the installation and go to the download page. I'm not trying to execute MSI from within MSI.)

Are you sure you want to exit the installation? We warn about missing required external components at install, then check at application startup & disable functions requiring them. Our unattended batch services do the same startup check and log an error if not found, then exit gracefully.