Cocoa-Text (Auto-completing fields)

I am trying to write code that auto-completes information from a database.
I am able to do to get the string I would like to use for auto complete.
Does anybody know what it is called when the browser completes your "www."
with "www.yahoo.com" and the ".yahoo.com" is hilighted in blue.

I am trying to achieve this with NSTextField, is there a better way.

 

I figured a way out

I still have a hard time describing what i wanted to do, but i figured it out. At first i was trying to use NSTextField, but that class only lets you select all of the text at once, but i found that NSTextView has a method setSelectedRange:
that does exactly what i wanted