Derice 0 Junior Poster in Training

Let say i hv two textbox, i.e. TextBox1 and TextBox2 and a button. Is it possible for me to write text into either Textbox1 or TextBox2 when the focus is at the textbox and button is clicked subsequently?

For example my focus is now at TextBox1 then i clicked on the button. TextBox1 is filled with "abc".

Is it possible for me to do that?