Multi text select in a TextBox

Hi,
 Is there any option to select more than one word in a textbox? not selecting all the words ,only selecting needed words and they are highlighted in different color ?is there any possible to create like this in silverlight by using list to get the words from text box in list ,if the words are already added into the list means it should be removed from the list.let me know any other option other than using textbox in silverlight .
Thanks in advance