Javascript and TinyMCE (can't change .value or textarea with TinyMCE)

In a perfect world (with out TinyMCE) the following code works great:document.myform.textarea.value += '[MY_BB_CODE]';

With TinyMCE enabled on this page, I can't use the standard javascript. I googled around and haven't found any JAVASCRIPT-ON开发者_如何学PythonLY solutions that didn't require some TinyMCE plugin... I'm sure I'm not looking in the right places, but has anyone here ever come across this issue?

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You can also do

tinyMCE.get('tinymce_id').setContent(my_new_content);

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tinyMCE.execCommand('mceReplaceContent',false,TextToAdd);