[Javascript] How can i create new <OPTION> elements of a visible <SELECT> element from a hidden <SELECT> element ?

[javascript@xxxxxxxxxx (M. Amin)]

Dear All,
  I'm developing a web site and i've a case in which i want to create a
hidden <SELECT> elements which its <OPTIONS>  elements set dynamically
and i've a main visible <SELECT> element in which i want its selected
<OPTION> element triggers one of the hidden <SELECT> element.

I'd like to share any good ideas about this case or anybody had implemented
it before i'll appreciate his help.

Any help will be Appreciated.

Regards,
 Mohammed Amin