[wix-users] Setting install dir path via custom action, works, but value changes back to default

[Alon Dean]

I'm trying to create an msi installer that will install the application to
the console session's local app data directory, even when the session that
runs the msi is the system session (when deploying via GPO).
For that, I'm creating a custom action that extracts the 'right' local app
data directory (this code works, no issues there).
The custom action will set the value of a property called 'INSTALLDIR'.
This is the relevant code from the wxs:

<Property Id="INSTALLDIR" Value="C:\Users\default\AppData\Local\"
/><Directory Id="TARGETDIR" Name="SourceDir">
    <Directory Id="INSTALLDIR">
        <Directory Id="APPLICATIONFOLDER" Name="MyApp">
        ...
<Binary Id="MyCA" SourceFile="My.CustomActions.CA.dll"/><CustomAction
Id="MyCASetLocalAppData" Impersonate="no" BinaryKey="MyCA"
DllEntry="SetLocalAppData" Return="check" />
...
<InstallExecuteSequence>
    <Custom Action="MyCASetLocalAppData" Before="CostFinalize">Not
Installed OR UPGRADINGPRODUCTCODE</Custom>

In the install log, I can see the INSTALLDIR's value change from the initial
value to the right value from the custom action, but later on in the log,
the INSTALLDIR's value is the default value again.

It seems like I need to call the MyCASetLocalAppData multiple times...

How can I fix this?

Thanks!