textbox focus check

I have a win app form with 3 text boxes and buttons as dial pad (it's a touchscreen app)...

When a dial pad button is pressed I want to check which one of these 3 text boxes has focus, and append text to it.

Something like:

if (tbx1.Focused == true)
{
   tbx1.Text += "0";
}
else if (tbx2.Focused == true)
{
   tbx2.Text += "0";
}
else
{
   tbx3.Text += "0";
}

But this doesn't work... It appends text to tbx3 all the time. Any suggestions?

Thanks :)