You can't, it just doesn't support it.
I have to ask, why those calculations need to happen Only inside the flash app?
You have to be navigating to an URL that clearly relates to the metadata you get from the flash app. Otherwise how would the flash app know to get the values depending on the URL you hit.
Options are:
re
Why is this upvoted? It's wrong. You CAN - it IS supported to add custom title, description and images to your share. I do it all the time. – Dustin Fineout 3 hours ago
The OP very clearly stated that he already knew you could serve that from a page, but wanted to pass the values directly to facebook (not through the target page).
Besides, note that I gave 3 different options to work around the issue, one of which is what you posted as an answer later. Your option isn't how the OP was trying to do it, its just a workaround because of facebook restrictions.
Finally, just as I did, you should mention that particular solution is flawed because you can easily hit the URL size restriction.