How can I set a text field to convert all text entered to proper case when populated within the same textfield?

[Michelle3799]

I am trying to get the entered text to auto change to Proper case within the same field. I started with the following script and it doesn't work.  Can you please review and advise.  thank you.

topmostSubform.Page3.Lastname::exit - (JavaScript, client)

  Lastname.rawValue=js.capitalizeEachWord(this.rawValue);

topmostSubform.#variables[0].js - (JavaScript, client)

function capitalizeEachWord(str)

{

  var words = str.split("");

  var arr = Array();

  for(i in words)

  {

      Lastname = Lastname.chrAt(0).toPropperCase()+Lastname.substring(1);

    arr.push(Lastname);

   }

   return arr.join("");

  }