Run powershell script in wix installer before install

I would like to run a powershell script before the install phase in a wix install project.

I can successfully run a script after the install, because the script is already there. I would like to embed the script in the .msi file, and reference it during the installation, but before it is installed.

This would require referencing the script from within the .msi file, or from a temporary copy. I can't figure out a way to reference files in the database before they are installed during the install phase.

From looking at the log file, I can see that the installer sets a 'DATABASE' property with a value that references "C:\Users\username\AppData\Local\Temp\nnnnneff.msi". I'm thinking this is where the installer is creating the database for the install. It would seem that the file would be there, and that perhaps I could reference it somehow.

    <CustomAction Id="CA_RunPreinstallScript"
                  BinaryKey="WixCA"
                  DllEntry="WixQuietExec"
                  Execute="immediate"
                  Return="check"
                  Impersonate="no" />

    <SetProperty Id="CA_RunPreinstallScript"
                 Before="CA_RunPreinstallScript"
                 Sequence="execute"
                 Value=""[POWERSHELLEXE]" -NoLogo -NonInteractive -InputFormat None -ExecutionPolicy Bypass -NoProfile -File "$(var.ProjectDir)\Resources\PreInstall.ps1"" />

    <InstallExecuteSequence>
     <Custom Action='CA_RunPreinstallScript' After='InstallInitialize'></Custom>
    </InstallExecuteSequence>

This example doesn't work. The -File parameter is pointed to a hard location on my system, instead of referencing a script within the installer file.

Is there some way to reference a file buffered in the database and use it as the -File value in a powershell custom action?

(There are a number of questions that address this, but I didn't find a real answer anywhere.)

I ended up creating a C# Wix Custom Action project in my solution and created custom actions. This type of custom action can be called anywhere in the install sequence, even before the User Interface sequence.

There are limitations on what 'session' data is available depending upon where the custom actions are inserted, but it creates a powerful way to interact with the install process.

I can insert a Custom Action created in C# before the installation starts, and detect legacy installations, and tailor the new installation based on the starting conditions. I can also run actions later in the install to handle details after the installer finishes modifying the system.