Not bad, it works fine as a calculator.
May i suggest a few improvements?
1. don't use textNumber as a variable. Instead, create two storage floats for the main display.
When user enters a number, it shows up. Then when they hit */- or +, have it display a second float variable, this will display the next numbers they put in. Then, when they hit =, apply the math to the first float and display that again. Now if they hit x or / again, we already have float 1 displayed, so you do the same....new entry becomes float 2, display that, and do the math to float 1 again, then display that when they hit =.
in this way, you can save both floats, so if they type 1+1= and it displays 2, like a normal calculator, you save the last function called (+-*/) and if the user keeps hitting =, it keeps performing the same math. so 1+1========= will display a final result of 9.
By using two float variables for the numbers, not only can you keep reusing them, but you can add a quick save/load list, where they can drag the text display to the save list or from the save list back to the display.
If you add such a thing.....you will actually have built a BETTER calculator than most, not just a working one, but a BETTER one.
2. Add a bevel filter to those buttons! Make them juicy and real so the user wants to click on them.
GIMP and Paint.net can both do a simple square bevel quite easily.
Only make 1 button (with no text on it)! Then distribute it (as i showed how in the post for bloodraven's calc)
viewtopic.php?f=6&t=7469and have ge write text numbers on the buttons.
Dim the rgb or transp of the button when clicked, so the user is sure their click was registered. (and the button goes back to normal after 1/2 second).
Its a little more coding, but you only have to make 1 button! (that's like, 12 buttons less than what you'd have to make if you put the numbers on them in your paint program).
And then, like my calc, you can make skins for it.