Forum:Chains on summons

Sorry for my English.

My opponent summoned Prime Material Dragon, in response to that summon I activated Trap Hole, my opponent chains his Prime material Dragon second effect to my trap discarding his only card on hand.

In response to that i tried to chain Torrential Tribute, but he says that i can't do that because i already activated in response to his summon and other effect is in play already, so in can't chain to the summon again. I understand that although the former is true, the latter not as the chain has been not resolved yet, so i can still activate in response to the summon as it was the last thing to happen on field, or am I in the wrong?