How to implement such an "Enhanced" drop down list component ?

[Andy Chu <an...@gmail.com>]

Dear All,

Suppose now we have a drop down list displaying description of each option.
There is also a TextField placed in front of the drop down list displaying
the option code.

Users can select an option from the drop down list and the code
Field will be filled by the corresponding option code automatically. 
On the other hand, users can input corresponding option code in the code 
Field and 
the drop down list will display the corresponding description immediately 
too.

It may be implemented by using javascript. I am not an expert at javascript.
I hope some of you would give me help or hint.

Best wishes, Andy