How to add new button (beside min, max and close) to the right side of a caption bar? Any hints?

I want to change the look of minimize, maximize and close buttons in the upper right corner of dialog or window. Also I am interested in code using skins. Does enyone know some good links and info I could find on the net? Thanks in advance.

Part of my project is to search/replace or add text in large text files (over 4MB). The sequential approach seems to be very time consuming, therefore I started to think about other methods/procedures. Do you have/know any suggestions, www links, code snippets where I could start from? Thanks in advance, Stan