how to create multilingual textbox

[Micheal]

Hi,

I have a dropdown list in the page in which different languages are add like
(german,english,spanish,french)

and other control is textbox .

i need to do when the user select 'German" language from the drop down list
then the textbox allow to write German only.

and when the user select "French" from the drop down list then the textbox
allow to write french only


please tell me immediately how i can do this . if anybody can provide me
step by step solution

or give me a detail code

it will great helpful for me.

regards

Micheal