Customize "ToolbarSets" in editor page

I want to set some configurations in editor page without altering the original fckeditor.js and without using a custom configuration file. I want to configure FCK in this way:

var oFCK = new FCKeditor('abc');
.... cfg options
oFCK.Config['DefaultLanguage'] = 'fr';
.... other cfg options
oFCK.Create();

Anything works well except configuring the ToolbarSets array. I cannot figure out how to add/edit a toolbar set from the editor page...

I had tryed:
oFCK.Config.ToolbarSets['MyToolbar'] = [['Source','Cut','Copy']];

but no chance...

Ant help will be welcomed!

Claudiu