Workflow aproval

My friends, anyone tell me, How I can creat one Workflow aproval on my app?

I have the loguin for de Admin and the other users.
So… when the Admin send the invitation for one event, He will invate for two users for exemple.

I would like that the users receive the information and the Admin see in your scream if the user accept or reject the event.

It seems like a fairly straight forward idea, just update you back end dBase accordingly.