Hey, James...
The file_selector() function does most, but not quite all, of what's
possible by directly calling the Win32 function for an Open/Save
dialog. That's part of what would make me hesitate to switch to doing
the Win32 call, since it would involve a bunch more work just to
accomplish the same thing as you're doing right now with just a single
line of code. However, so far as I can tell, that's probably what it
would take to accomplish this, other than doing something like a
custom XUI, which would also be a fair bit of work, but possibly of a
more comfortable sort, depending upon your tastes.
If you're interested in the Win32 route, the function you'll want to
look at is called GetSaveFileName. It requires reading and writing a
structure, which you can do with the unpack() and pack() functions,
respectively.
-Brandon 🙂