How to create my own custom action in Microsoft Outlook Rules?

In Outlook, when creating a rule in the Rules wizard, we set first the conditions and then set the actions that we choose from a list of predefined actions. Is there a way to add my own action to the existing actions programmatically?

I also see an action called custom action, when i click it it opens up a small window with an empty combobox, can i add my custom action there, and how?