I have used ChatGPT for things like creating very specific and technical functions, which I then adapted for use in Roll20 scripts, but there is just too much that is specific to Roll20 for it to have general use. It does not know the structure of Objects in the Mod System, the syntax of Roll20 functions, what constitutes an Event, and much more. Also, Even if you were to build the script you envision, it could not link directly to the Roll20 chat box (without a highly-specialized browser plugin, requiring knowledge of both Roll20 (which runs in its own sandbox) and ChatGPT's API. They cannot "talk to each other". And if it were, it might not even be legal due to licensing.