How can I make sure to get a storyline mission from a specific corporation?

I'm trying to get some better standings with the Amarr Empire and the Emperor Family corporation to reduce the broker fees when trading with my alt. This is already a rather annoying process, and receiving storyline missions from the wrong corporation makes it even slower. The storyline missions are responsible for a large part of the total standing gains, I don't want to waste them on a meaningless corporation.

How is the corporation for the storyline mission determined? How can I make sure to receive a storyline mission of the same corporation I'm running missions for? How would this work specifically if I want to gain standing for the Emperor Family corporation and can only fly distribution missions?

Storyline missions are obtained after competing 16 missions of the same level for the same faction. The storyline mission will be offered by the closest storyline agent of the same faction (not corp) to the location at which the 16th mission was completed. Ties for closest agent are broken randomly.

It's also very important to note that storyline missions are not guaranteed to be of the same type as the missions that were run to trigger it. Its entirely possible for you to get multiple security (combat) storyline missions while running distribution missions.

Source: the E-Uni wiki page on missions