MUI Install Options

Is there a way to skip the directory selection screen if the application is already installed and just need to be upgraded?

If Not AppInstal Then
!insertmacro MUI_PAGE_DIRECTORY
Else
End If

Call Abort in the pages' PRE function to skip that page.

-Stu

you have to use page's pre function.
see NSIS documentation, for MUI is MUI_PAGE_CUSTOMFUNCTION_PRE "your function".