Visual Basic .Net programming?

I need some istance please. I have the user inputing a string. They then enter a number and click a on and the program will display the word from the string they entered that correlates with that number. (i.e. the user enters "I LOVE YOU" then "2" when they click the on "LOVE" appears in the textbox. How do I separate each word when I don't know how many words the string will be?