How to mask characters in TextBox (Windows Phone) -

i have been looking method mask characters in testbox coudn't have found.

i have use textbox, beacause have implemented validation styles previous question.

ps. have read question: http://outcoldman.com/en/blog/show/308 there nothing import class

do have ideas how mask characters?

get this:

passwordbox control: http://www.bondigeek.com/blog/2010/03/29/windows-phone-7-dev-series-textbox-input-scope/