I\'m writing a plugin which will convert emoticons to images in a text block for a particular site. The easy answer is to use regular expressions to detect the trigger text
If I understand you correctly, you want to convert say ":)" to an emoticon. To do that, you need to parse the text and replace those characters with an img element. So you want to do something like:
here is a smily:) and another two:):)
The above needs to be modified to deal with multiple different emoticons in each text node, but I think you get the idea.