Judging from the handler declaration you are using a very old version of our controls (over 5 years old) and it is simply possible that these buttons are not implemented yet in the version you have. You can easily confirm if this is the case by downloading a trial of the latest version to see if it has the functionality you need.
. Here is a list with the commands: http://www.telerik.com/help/aspnet-ajax/editor-toolbar-intro.html
and you can see the spellcheck command name.
What I can suggest for disabling spellchecking is checking the jQuery selectors you use and whether they return the expected arrays. At present, the tools can be distinguished by their title attributes and the class on the inner span. I would advise examining the rendered HTML in your browser to see how to access them.
A better approach would be, however, would be using the OnClientCommandExecuting event (http://www.telerik.com/help/aspnet-ajax/editor-onclientcommandexecuting.html
) to cancel the spellcheck process according toa custom flag you can raise with your checkbox:
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