jQuery - 在tinyMCE iframe之外的div中添加css类？

I want to add a tool-tip to a tinyMCE editor when a user focuses into the editor and hide the tool tip on blur. The problem is tinyMCE injects an iframe but the div i want to add the css class to inorder to toggle the tool-tip resides outside of the tinyMCE iframe.I want to add a tool-tip to a tinyMCE editor wh