Add date range to XML

Hello,

You’re plugin is really amazing! But I have one little problem. In my XML I need date range for my export. I export orders for yesterday (every day) and I need something like that in the beggining of XML: <OrdersForPeriod from=”{date_From}” to=”{date_to}”/>

I was trying to write few functions but everytime I’m getting error. Is possible to achive something like that?