Help with combat

I need help with a combat scenario. The player needs a special weapon, in this case, a Dagger of Slashing, to kill an enemy. If he doesn’t have the weapon, the enemy kills him if the player doesn’t attack or leave the room. How can I pull this off?
Any help would be greatly appreciated.
Thanks!

This thread (https://intfiction.org/t/npc-wait-to-attack-error/4173/7) and 130 and 282 in the Recipe Book should help.