Textarea filled from dorpdown

Hi crew..

It's possibleto fille a textbox area with the choice made in a dropdown element??
I try to explain better..
I've a dropdown (multiselect) element (id=> dropdown) filled with data from db table.
Tha data in dropdown is like

value - - - Option
1 case 1
2 case 2
3 case 3
etc etc..

I also have a text area element (id=>textarea) which is empty.
I would like (if possible) to fill this textarea with the dropdown multiselection
eg

case 1
case 3

So.. I think to use an ACTION named prova with a custom element with the php code

<?php
$form->data["textarea"] = $form->data["dropdown"];
?>

and set in dropdown element an EVENTS like

[!=] [] [set dynamic option] [textarea] [prova]

but.. obviously.. it soes not work...

ho can i do??

Regards and thank's

OK ok ok... i do some test and now can fill a textarea box with data selected in a dropdown box (multiselect).
And work fine...
Now i would like to do another step..
Insted of a textarea, i've a custom field with this code (thanks to Max Pain!!!)

<?php
$editor =& JFactory::getEditor();
$params = array( 'smilies'=> '0' ,
                 'style'  => '1' ,  
                 'layer'  => '0' , 
                 'table'  => '1' ,
                 'clear_entities'=>'0'
                 );
echo $editor->display( 'custom', '', '50', '50', '5', '5', false, null, 'asset', 'author', $params );
?>

which load joomla default editor.
Well.. It's possible to fill this editor (loaded in custom field) with the dropdown selected value??

Hi giacall,

That's probably possible. You'll need to check the Editor documents to see how to set the value; then add JavaScript so that the value is set when the drop-down value changes. Note that if you do that then if the user adds content it will be lost if they they change the drop-down setting.

You can get an idea of the code needed from this FAQ

Bob