You will have to spend time studying the scripting guide and the AE SDK.
I doubt you require an exe file to do this. It's a lot of work to create an exe file.
You can have AE load a specific project each time it opens. AE's Preferences Dialog has a section called New Project. In this section, you can open up a specific file/template. Then, you need to autoload a script by using the Run command in AE. I'm not certain how to get this done but the folks at aenhencers.com may be able to help you out.
Not sure what you try to achieve with this. Why would you want an executable with a button if you can use 'replace footage' in AE.
You only need automation if you need to watch a folder for a png to appear which automatically generates a video out of it; no buttons required. But if there needs to be someone to click a button, he can just as well click 'replace footage' and 'render'.