Custom Fck Editor for add shadowbox option

Hi everybody!...
first, sorry for my english...
So, I have 2 problem :

The first :
I add an option and remove other option in fck_link.html > <select id="cmbTarget"...> like :

<select id="cmbTarget" onchange="SetTarget(this.value);">
   <option value="" selected="selected">Aucune</option>
   <option value="popup">popup</option>
   <option value="shadowbox">shadowbox</option>
</select>

in fck_link.js > function Ok() , I add this :

if( GetE('cmbTarget').value == 'popup' ){
   onclick = BuildOnClickPopup() ;
   // Encode the attribute
   onclick = encodeURIComponent( " onclick=\"" + onclick + "\"" )  ;
   SetAttribute( oLink, 'onclick_fckprotectedatt', onclick ) ;
} else if ( GetE('cmbTarget').value == 'shadowbox' ) {
   SetAttribute( oLink, 'rel' , 'ShadowBox' );
}

When I choose shadowbox in the target list, the rel="shadowbox" is present in <a href...>.
my probleme:
when I edit the link, the title and Url (...) is set in form... but not for shadowbox...
How I can force selected <option>shadowbox</option> ?


The second :
In image propriety, i would add a checkbox for use shadowbox.
The user choose image : toto.jpg
the result is :

<img src="toto.jpg" />

if the user check the shadowbox checkbox, fck must add "thumb_"+filename in <img...> and add <img...> in a <a href...>
exemple if user choose "toto.jpg" :

<a href="toto.jpg" rel="shadowbox"><img src="thumb_toto.jpg" /></a>

if you have an idea, or an script for make this ...

Big thanks !