Simulate User of App with VB

OK...I don't know where to start to look.

I am writing a program that will take control of a program that is already running on the desktop and enter some information and submit it.

Currently, they user has to click on buttons and enter information into fields, which I want to populate from a VB program that is running. I want to either tab onto the buttons and simulate the enter key and then move the cursor to the textboxes and enter information store in variables. Does anyone know where I can start to look for help on this or know what I would look for help. If you need more info, let me know.