Digvorzhak, King of Heavy Industry

this card effect:
3 Level 5 monsters
Once per turn: You can detach 1 Xyz Material from this card; send the top 3 cards of your opponent's Deck to the Graveyard, then, if any monsters were sent to the Graveyard by this effect, destroy cards your opponent controls, up to the number of monsters sent.

the problem its: i active the effect, if there no monster discarted they dont active effect (ok), but if discard they dont let you see the graveyard for know how many cards you can destroy

i think i good solution will be a mini screen that say something like this

Digvorzhak, King of Heavy Industry discard (number) monster cards, you can destroy up (number) cards that your opponent control

or let see the opponent graveyard while you can chose targets for destroy

sorry i bad in english