I've been developing a series of simple quests using the Creation Kit (I'm kind of new to TES modding). For one quest, I would like to force the player into a dialogue sequence once the player is within a certain distance from the target NPC of the quest. I assume I'll have to use the GetDistance command between the player, but what command can be used to start a dialogue branch?

Any help is appreciated.

Edit: My goal is something similar to when the player encounters the Emperor at the end of the Dark Brotherhood questline, where a short dialogue sequence is started.