Create a base “Button” actor with a variable to store your button number and have your keypad numbers inherit from this actor. Add these new buttons to your keypad, changing the number variable for each one, respectively. From there, you can use [Is Clicked] nodes to determine if your player has clicked on this actor. It’s important that the [Is Clicked] be triggered in reference to that button’s instance because you would otherwise keep triggering the original instance.
I highly suggest checking the trigger from the keypad’s blueprint, using the events that trigger when a child actor of this actor is clicked. Then, you can simply check the button number using a reference to the child actor that was clicked. If need be, add another text component to the keypad and add asterisks for each key press; the actual number can be appended to a hidden/private variable, in the keypad actor, that doesn’t send to the other players.
[Edit]: As a side note, you could use [Get Hit Under Cursor by Channel] in your mouse click event graph. From there, you would use [Break Hit] and pull the (Actor) pin to check which object, or actor, was pressed. IMO, this is not the right approach when you could have the keypad handle clicks on child actors.