Transition surface

Dear Guys,

Sorry, I accidentally sent this question before I was created it!
I would like to find a way I could make a transition surface between two surfaces defined by wires. I attach a picture about what I want, can anyone help me by explaining a process I could build up the green surface? The tangents of the surrounding surfaces should be imposed, so a perfectly smooth shell is what I would like to build up from 3 surfaces. Is there an effective way to make that?

Thank You,