Cutting Words timing when playing online


Lore Bard’s Cutting Words feature states the following:

Also at 3rd level, you learn how to use your wit to distract, confuse, and otherwise sap the confidence and competence of others. When a creature that you can see within 60 feet of you makes an attack roll, an ability check, or a damage roll, you can use your reaction to expend one of your uses of Bardic Inspiration, rolling a Bardic Inspiration die and subtracting the number rolled from the creature’s roll. You can choose to use this feature after the creature makes its roll, but before the DM determines whether the attack roll or ability check succeeds or fails, or before the creature deals its damage. The creature is immune if it can’t hear you or if it’s immune to being charmed.

What exactly does that mean. At what time do I have to say my DM I interrupt them?

When playing at a table, my DM usually goes this way: “The goblin attacks [player character] with their bow and [rolls] hits”. I can hear the dice roll and I say I want to know the result in order to decide if I want to use Cutting Words.

Now with the current sanitary situation, we play online, and the DM usually rolls their own physical dice and tells whether it hits or not because they have all our ACs registered. This basically forbids me to use my Cutting Words.

So what is the exact timing where I can interrupt the DM, online, and use my Cutting Words?