Access gui components of 3rd party app

[mc1982]

Hi,

I made a small application named myprog with a text box and a button, when your press the button it checks if the text box has the value 1234, if it does it dissables the text box.

Now, i want to write a 2nd program that will be able to enter into the myprog text box and press the button.

Can someone point me into the right direction or topic to look under for a way to enter things into another programs text boxes and press buttons?