C# beginner question about automation

What i want to do is make a program that responds to a different program. If a box pops up i want my program to respond to that box that popped up. If i get a connection drop from the program i would like my program to auto matically reconnect and click on the proper button. This is what i am trying to learn but not sure what book to read or where to get more information about how to do this. The program does not have a SDK or any code that can be revealed at all. So i decided to try and make it automated as if i was there in front of the computer doing the work. If anyone can point me in the right direction or help me out in anyway i would appreciate it. Thank you.