Trigger action ONLY while mouse clicked

When creating a Automation/Named/Other Trigger, there is an option to Allow trigger while mouse clicked and an option to Trigger only while holding these keys. But what I really want is an option to Trigger ONLY while mouse clicked. For example, I'm not a huge fan of hot-corners-all-the-time, but it would be useful if I was dragging something to a corner specifically to trigger a custom action. Unless I'm missing something, I currently have to get my keyboard involved to achieve what I want.