Hello Steve and welcome to Advanced Installer forums,
Thank you for yor interest in Advanced Installer.
In order to achieve what you want you can import the related merge module in your Advanced Installer project. Just open your project, go to
"Home" tab an using the [Import] button select "MSI/MSM Package" option to import your MSM file. Then, you can go in "Files and Folders" page and remove the imported merge module file and add your current file.
Another approach would be to add you current file as a
temporary file and, then develop your own
custom action which will overwrite the file installed by the merge module with your current file added as a temporary file. Also, the custom action should be scheduled after "Install Execution Stage -> Add Resources" action group and should run as deferred with no impersonation.
If you have any questions let us know.
All the best,
Daniel