tour_progress_effect

tour_progress_effect = {
	# Progress the activity
	if = {
		limit = {
			scope:activity = { exists = var:months_of_stop }
			scope:activity = { var:months_of_stop >= 2 }
		}
		scope:host = {
			save_scope_as = visiting_liege
			location.province_owner ?= {
				save_scope_as = stop_host_scope
				if = {
					limit = { has_character_flag = being_visited_on_tour }
					remove_character_flag = being_visited_on_tour
				}
			}
		}
		trigger_event = tour_general.0510
	}
	if = {
		limit = {
			scope:activity = { NOT = { exists = var:months_of_stop } }
		}
		scope:activity = { 
			set_variable = {
				name = months_of_stop
				value = 1
			}
		}
	}
	else = {
		scope:activity = { 
			change_variable = {
				name = months_of_stop
				add = 1
			}
		}
	}
}

As written in game/common/scripted_effects/04_dlc_ep2_tour_effects.txt.