add code to generate filename to existing "Save As" button

Hi. I created a pdf version of a standard form we use here at the office. One of the users is very, very much a computer novice and simply saving and renaming is a challenge. So, I put a shortcut to the form in the folder where the created forms need to be saved (so that is the default save location) and created a save as button on the form, but I'd also like to automate the save as file name.

I have this code under the "mouseup" event:

app.execMenuItem("SaveAs")

_3c5o2408p3b4a69j3o.pdf

Any ideas what I'm doing wrong or missing OR what might be a better way to skin this cat?

Thanks!