A file with the .vlx extension is a macro application written in AutoLISP dialect of Lisp programming language integrated to Autodesk applications such as AutoCAD. It is also known as Compiled AutoLISP File. VLX files are compiled AutoLISP files that were created with Visual LISP. They contain multiple routines and can be used for creating macros that can be run within AutoCAD
To open a .vlx file, you need a suitable software like AutoCAD from Autodesk, Inc. Without proper software, you will receive a Windows message “How do you want to open this file?” or “Windows cannot open this file”
To load a .vlx file in AutoCAD, you can drag+drop the .vlx file from Windows Explorer onto the drawing editor. You can’t unload them in the same session. Shutdown and restart AutoCAD to unload1. Alternatively, you can add your .vlx files to be loaded within your acaddoc.lsp file. These .vlx files will be loaded every time you open a drawing automatically
To check the file content use Notepad++ and select from programming lanuages ====> LISP
I hope it can help you