|You can use the ReplaceNoCase function, or a Regular Expression using REReplace.|
The Replace would look something like below.
The only disadvantage of this is that it will highlight the word as a substring (which you might want to do if your search is returning it that way anyway).
The Regular Expression could search for the search term as a whole word (surrounded by spaces) in similar fashion.
Another option would be to use CF_Highlight or CFX_Highlight. Both are free tags available from the tag gallery.