Chaining cards from the hand to Wind-up hunter

This situation arose in a game I had on DN I just wanted to make sure that I was right.
I used Wind-up hunter's effect to send a card from the hand to the grave, my opponent wanted to chain the card I selected (clicked on), which was a D.D. crow. I said that he would have to chain it to the activation of hunter's effect before I selected the card so another card would be sent instead because hunter selects the card at resolution. Is all this right?

Hunter's effect:
You can Tribute 1 face-up "Wind-Up" monster, except "Wind-Up Hunter"; send 1 random card from your opponent's hand to the Graveyard. This effect can only be used once while this card is face-up on the field.

D.D. crow's effect:
During either player's turn: You can discard this card to the Graveyard to target 1 card in your opponent's Graveyard; banish that target.

These cards have to be used before any card in the hand is chosen. Read Hunter's text.

Choosing cards in your opponent's hand is a random process, which means it is done at resolution. You cannot activate any effects during the resolution of an effect.

Thanks, this happened in my game for the war against Marshmallonforthewin, he thought you could chain after I selected and after a few minutes of trying to explain he finally let me continue but he did not seem happy about it.

Don't try to explain things if your opponent doesn't understand for that reason is the admins next time do not sit trying to get them to understand the simplest thinks just call an admin

It was in unrated for the war so I could not call an admin or quit . But he agreed with me after a while.