Find And Replace Script For Dreamweaver?

I'm often creating html for foreign languages [from supplied copy] which uses special characters eg graves, umlauts, etc. As a matter of routine I replace the copy text with the correct document character eg for a u with an umlaut, I replace it with &# 252;

I do all of this in dreamweaver and it can take ages doing a Find and Replace on each of these special characters.

I've read that you can create a Command in dreamweaver which basically executes some javascript you saved in an htm file.

Can anyone show me the code I'd need to add to an htm file so I could run it as a Command? Basically I just want it to go through the entire html file I'd have open in Dreamweaver and replace all of the special characters it finds with the correct &#... alternative. Would be even better if it could also tell if you've just selected a portion of the text and do the Find and Replace on that.