Vista - Vista context menu question

Is it possible to add a context menu item that, when you right click on a file and choose your new item, it will rename the extension of the file you clicked on to a preset extension such as txt.

Example: right click on a file called test.log and choose your new menu item which we will call "change ext" and the file will be renamed test.txt .

If this can be done in the context menu, please advise how. Please don't tell me to just right click and choose rename from the menu. Thanks in advance. Ras