hi pilotsredlix,
CuteEditor has not provide the way to set the marquee target properties directly. So I think you need to remove the old target and replace it with the a new one.
How to get the selected html http://www.cutesoft.net/developer+guide/scr/Get-HTML-from-Selection.htm
And use API "PasteHTML()" to replace the selected html http://www.cutesoft.net/developer+guide/scr/JavaScript-API.htm
Also, you can get the editor document object and find the <marquee> target by the document object. Then you can change its properties by javascript code. The editor document object has the same functions as the normal html document object.
Regards,
Ken