Sorry for my late reply, we are in national holiday. To do this you need to register the keypress event and allow only number to be passed. Something like this:

TextBox::create(array(
    ...
    "clientEvents"=>array(
        "keypress"=>"function(event) {
           $(this).val($(this).val().replace(/[^\d].+/, ''));
            if ((event. Which < 48 || event. Which > 57)) {
                event.preventDefault();
            }
        }"
    )
    ...
))

Note: My code is just to represent the idea

Hope that helps.

May be you try this code for decimals number:

"function(event){
     $(this).val($(this).val().replace(/[^0-9\.]/g,''));
            if ((event.which != 46 || $(this).val().indexOf('.') != -1) && (event.which < 48 || event.which > 57)) {
                event.preventDefault();
}"

That's great :D