Well no I want the actor basically saying "Hey you there come over here". Not force a greet with the player.
SImilar to the crazy wood elf in Skingrad in Oblivion.
Make a new branch in the Dialogue View tab, then double click the branch and make it Blocking. Then, set conditions so it can only be said when you want. (With a GetIsID, and a GetStage, perhaps) Then make it a goodbye. Or, if you want the NPC to actually be able to speak with the player, dont make it a goodbye, and link it to the actual dialogue. Then he will say 'Come over here' when the player stands near, and when the player activates him, he'll say that. Then, if you want him to instantly jump into the rest of his dialogue, double click the link from that line and the next topic, and say Make Invisible Continue. Click OK to the warning that pops up, and you're good to go. He will now repeat that one line if the player is near him, and when activated, he will say it, then continue speaking the rest of your dialogue.