Executing a dll before Welcome window appears

Is it possible to execute a dll before the Welcome window appears? I want my form written in C# appear first in the installation.

THANKS!!

I advise not to use a .net dll when installing if the application will run on machines since you do not know if .net is available.

If it is for internal use, you can offcourse 😉

You could also create a NSIS plugin with Delphi or C that runs the code you created.