(keitai-l) Is it possible to limit user input to numerals on iMode and Jphone?

Hi 

I'm trying to limit user input on iMode and Jphone phones too fill in an
input field with numerals.

Currently we have the following code...

On imode

<input type="text" name="phone" maxlength="11" value='12345678987'
istyle='4'>

On Jphone

<input type="text" name="phone" maxlength="11" value='12345678987'
mode="numeric">

 

But the user is still able to change their input style to "kanji" mode
or "katakana" mode.

Any ideas?

Jonathan