Marc is correct, there's no way to hook into the existing export to spreadsheet functionality.
You can however build your own. It's a big task, but doable. You would have to create your own function in code (as an event handler) to take the contents of a list and pump it into a spreadsheet. That spreadsheet can be your own making, including any VBA script or macros.
Then you would have to craft some ribbon UI modifications to a) hide the existing Export to Spreadsheet and b) surface your own version.
Lots of work and things to watch out for like name collisions in the menu items you create, but all doable. The question is it worth the effort? For something that can be as big and complicated as this I go back to what you're trying to do with the data and come up with a different solution to the problem. Perhaps a custom view or event handler can do what you're trying to accomplish.