Andre,
the script is completely from "top to bottom". What you see in the script is what you get at installer runtime. So if you move your "Run Program" action to a place before the "Install File" action then it is executed before the file installation process. BTW, make sure that you have "Run program once the installation exists" in the Run Program "Finish Dialog" tab disabled. And you should "wait" until the external program has finished. Otherwise, the installation continues immediately.
Friedrich