DYYNAMIC STAMP IDENTITY PREFERENCE ISSUE

Please, how do i pull the identity organization unit from the preference window?
i changed my identity.name line to identity.unit from the below lines of code but it returns with undefined

if((event.source.forReal)&&(event.source.stampName == ""))
{

this.getField("Approved").value = identity.name;
this.getField("Date").value = util.printd("m/d/yyyy h:mm tt", new Date());

}

Kindly show me how to fix it

Thanks.