I've poked around in the registry and there's way too many values changing even just to show what's on the screen. Don't think this is doable. Like I can change it so that the game shows I have 4000 points, but when it sends it to the server my score is only recorded as what it would have been anyways, so there's probably a lot of values at play here. Even worse, considering the screen only shows single digits, 1-6, it'd be super easy to create a program so that the nice are never actually appearing as 1-6 in the registry, and instead have to be calculated.
One work around is that the diceset is the same every time until you click "PLAY", at which point it's on to the next dice set. So if you don't save any dice, don't click "PLAY" after your final roll, delete the game, and reload the game, sign back in, you know what dice are going to show up in which order.
Example (not saving any dice):
Throw one: 51223
Throw two: 55244
Throw three: 44422
So let's say I delete the game, reinstall, and now I roll.
Throw one: 51223
I save 1 and 3
Throw 2 will show: 51523
I save 5,1,2, and 3
Throw 3 will show: 51423
Congrats - you now have a large straight!
However, if you had played nothing on the first throw, saved your two 4s from the initial second throw, and then, on the third throw, you'd get 44444 - Yahtzee!
Takes a solid 20 mins to beat a dicemaster via this method, and that's with fast internet.