Calculator with visible decimal point on screen

Hi. I downloaded David Charney's calculator that he made, and it works great! The only problem is that when you hit the decimal point, the decimal point doesn't appear on the screen until you hit the next number after it. I need for the decimal point to appear in the box as soon as it is clicked. Is this even possible? I am attaching his download, but if anyone else has a solution, I'm all ears. Thanks in advance!