After logging in to facebook (Soomla plugin) instantly share a post with a captured image. How is it possible? (Unity3D)

In my Unity project there is a share button and if the user presses it and he/she is not logged in already then the facebook log in window shows up. And what I would like to do, is that after this login the "share a post" window comes up. (I would like to capture the games's image with the Unity API (Application.CaptureScreenshot("Screenshot.png");) then share that image) So it happens with just one touch on the share button. Is it possible? If yes, then how?

I want to use the Soomla plugin from the asset store.

Thanks, Gabe