New to CS - Process text between certain tags

Hi,
 I am new to CS, and have a quick question. I want to add a special tag in my templates for certain pieces of text. For example, I want to enclose text in tags like <special> and </special>. Then, I want to do special processing on these pieces of text when it comes to rendering this text. This processing will be happening in Java, before the page is rendered. Any pointers on how to achieve this?

Thanks a lot