I think you're looking for something like this: http://forum.unity3d.com/threads/12341-Validating-user-input

Converting that from C# to UnityScript should be fairly straight-forward.

-V

While it seem overwhelming at first, Regular Expressions can do all sort of complex string manipulations. You can allow/unallow any kind of 'expressions/pattern' from a string. You'll find lot of documentation and even lots of prepared RegularExpression out there.

OR you could manually validate it by comparing each input's character to a AllowedCharacters char array, or something similar.

OR you could use string.Replace("a",""); but this is tedious and will leave tons of unexpected characters.

Best bet is the Regex :)

It's definitely possible with JavaScript.

Sounds like you don't want to show a TextField, you just want to capture numbers. Can you just do something like this ?

var userInput:int;

if(input.GetKeyDown("1")){
    userInput = 1;
}
if(input.GetKeyDown("2")){
    userInput = 2;
}
//and so on...

...or am I misinterpreting your question?