ProJucer - Compile files for specific platform

I have a cross platform project (macOS and Windows) where I want some cpp files to be added to the project for only Mac and some for only Windows.

I don’t see an option for “Compile” based on the selected exported.

I’m sure I could create various wrapper cpp files to optionally compile files in but I’m hoping for a solution that I can determine which files are included for compilation on a per platform basis.

Am I missing something or is this not possible with ProJucer?