Facebook blue highlight for a multiline ASP.NET textbox

[Ethemesep]

I am trying to implement Facebook autocomplete functionality after a user types @ for a multiline ASP.Net textbox, including highlighting the selected text (this would only be a part of text inside the textbox).My question is: is it possible to apply different styles inside a textbox or how does Facebook highlight in blue what the user choose from the completion list? How can I achieve the same result with my textbox? As far as I know one cannot apply different css inside the same textbox.Please help & encourage me.