How do I make an OR block?

I want to make this kind of block:

event1

AND

event2

AND

event3A

OR

event3B

the event3 is tied to the first two events whether is event3A or event3B.

How do I do it?

event1 AND event2

->sub event event3A OR event3B -> action(s)

no wait, I meant

event1

subevent1

subevent2

OR

subevent3