Question regarding GuiTextEditCtrl

[Gunderak]

Basically I am working on a trade system.
I want to make it so that if you enter a character that isn't a number it will remove it. I have made the detection weather it is a number or not but how would I remove the last character of the textedit control?
I have tried a few things, such as:

PHP Code:

Trade_MyGralats.text.length() -= 1;
Trade_MyGralats.text.size() -= 1;
Trade_MyGralats.text -= 1; 


But none of them work, Thanks in advanced.
I was also thinking maybe it would have something to do with .pos() Not sure though.
Maybe this is an idea for a future improvement for text controls.

PHP Code:

allowedcharactersonly = true;
allowedcharacters= { "a", "b", "c" };