Here's some information from https://docs.appeon.com/pb2021/pbug/ug58941.html :
Tip
Advanced usage of External Files and Preload Event
The combination of External Files and Preload Event can streamline the process of deploying a setup package to the server, installing the package and registering the file on the client machine. In the External Files page, you add the folders and/or files that make up of the setup package, and in the Preload Event field, you add commands to run the setup file and register any component if necessary.
Take Microsoft OLE DB Driver for SQL Server (MSOLEDBSQL) as an example. Suppose the MSOLEDBSQL setup package includes the following folders and files: msoledbsql folder, sqlncli folder, CheckDBDriver.bat file, and Install.bat file.
Step 1: Copy the msoledbsql folder, sqlncli folder, CheckDBDriver.bat file, and Install.bat file to the same folder as the application target file.
Step 2: In the External Files page, select Files (Download at startup) in the list, and then click Add Folder to add the folders: msoledbsql and sqlncli and click Add Files to add the files: CheckDBDriver.bat and Install.bat.
The selected folders and files will be first deployed to the server and then downloaded to the application directory on the client machine.
Step 3: In the Run Options page, add the following command in the Preload Event field: .\CheckDBDriver.bat.
The command will be executed automatically when the application is first installed or upgraded. The CheckDBDriver.bat file checks whether MSOLEDBSQL is installed on the client machine. If MSOLEDBSQL is not installed, then Install.bat is automatically run to install MSOLEDBSQL. Administrator rights are required to run the Install.bat file, so the end user will be prompted for that if Install.bat is run.