Would you gonna use TextBox with Type = number (maybe you love the spinners) ...
And would you want the numbers limited to 0,1,2,3 or 4 (natural numbers, so 1.333 is not allowed) ....
.... Then you have to deal with a lot of exceptions.
First this, the TextBox.text expression can only contain numbers.
Yet, it accepts the characters "-" and "+" and "," and "." as input.
It shows them, but they will not be inside the TextBox.text expression, unless they form a number.
So
if you type "4+4" in the Box, TextBox.text contains something, but it is not the empty string ""
if you type "-" in the the Box, TextBox.text contains something, but it is not the empty string ""
if you type "-5", TextBox.text contains "-5", that is a number.
If you type "4.", TextBox.text contains something, but it is not the empty string ""
If you type "4.1" , TextBox.text contains "4.1", that is a number.
So. Again. The TextBox.text expression can only contain numbers, even if it is showing something else.
This is a modest attempt to catch the exceptions.
https://www.dropbox.com/s/qsi250afm5ie9 ... .capx?dl=0