I know of know way to make a particular word in a string interact with the mouse unless maybe that word is a hyperlink. I didn't interpret your first post that way.
I've never tried this, but AFAIK, your field would have to be formatted as rtf for a start, and those specific words would have to be wrapped in href tags, making them clickable - and that's an assumption on my part. Not sure if href is usable in a rtf field. If the field itself was hyperlink type it would attempt to make the entire contents a link.
I thought you wanted to look for a keyword in a field, not click on it and do something so I'm afraid I'm just speculating now. Sorry.