You could write your own one using a LOT of Javascript. Nothing known.
However, when you're talking about IE being required, I think I know what you mean, and I think that is not technically correct.
Such existing editors run on ActiveX objects, which are a Microsoft technology, and are native to IE. However, there are plenty of ActiveX plug-ins for Netscape nowadays -- just search Yahoo.
If you need tips on how to write this in Javascript, ask. I know how, just very tedious, but the system is simple. I would NOT recommend it, though. Look at how THIS poster here in the forum works -- I think this is the ideal 50/50 solution.