...
Silent install string: PASCO_Capstone-x.y.z.w.exe /s /v"/qn LICENCEKEY=MY_KEY"
Note while this appears to be incorrect syntax, this is exactly what's on their site and appears to work.
Silent uninstall string: msiexex /x <Product Code> /qn
Detection Method: %ProgramFiles(x86)%\PASCO scientific\Capstone\Capstone.exe exists