For me, variable. Its kinda easy, make a variable and then make a copy of the ghost monster. Then, add a event for the monster like...
>Conditional Branch when "ghost hp 0" variable "whateveryourvariablenameis" +1
Then, make an event for the dude, what he has to say and stuff and also, add one what is something like :
>Conditional Branch when variable "whateveryourvariablenameis" 10
>Message: "Whatever you want the person to say"
.
Sorry, I've been away from RMXP (haven't touched it for 4 months) so I can't remember the events clearly, but I'm pretty sure I went along the lines.
~Winged