Format string throghout OmniOutliner document using AppleScript

I would like to write an AppleScript to do the following :

Apply a specific format to every occurence of a given string (case insensitive) in all level-n rows in an outline.
For example, in every row of level 4, every occurence of the string “amp” should become blue, bold and underlined.

Is it possible ? If so, any guidance toward the right direction would be greatly appreciated.
Thanks in advance. W.