First you need to run an Extra Session you have setup, with the machine name, port etc. This session should be *.edp

I dont understand exactly what you want to do here....
but you can recognize specific mainframe pages using Extra, and kick off an Extra macro when a user goes to a particular screen, or even navigate between screens via a macro. (Extra macros use an older versin of VB - still does most things though)

You can get data from the screen using a Session object... something like this :
Sess0.Screen.GetString(1,1,10)
(first 10 chars from position 1,1)

I have some examples which do a few different things if you are still interested.

BG