How to set alignment of a TextFrame in illustrator using extendscript

Can't work this out or find any thing I can get this to work. I want to make the anchor point on a text object be on the right of the text (align right). have tries this:

if(item.constructor.name == "TextFrame") {

        item.textRange.ParagraphAttributes.justification = Justification.rightAlign;

}

but it doesn't work. Would anyone out there tell me what i'm doing wrong

Thanks