How can I get/set information from a Save As dialog of another application in c#/c++?

I want to make an application who can detect if the application that has the focus has a SaveAs dialog opened, and if the name of the file already exists to automaticaly change it into something else, and put the new name of the file in the SaveAs dialog of that application, so when I press save I will not get that message: "The file already exists! Do you want to replace it? "

How can I get/set information from a Save As dialog of another application in c#/c++?
At the API level, the operating system is designed to prevent applications from messing with each other's data. You might have more luck with a macro language, such as the type you use to automate common tasks.