How to load new (unknown) items from a XML file.

I wonder if anyone can give me any idea how to load new (unknown) items I have inside a XML doc.
Our designer want the functionallity to be able to "mod" our game by just adding new items inside the XML doc instead of having a fix amout of stuff.

At the moment it looks like this

Before new stuff is added

&lt!--- some other stuff -->
<goods type="goods" name="food" tooltip="Used for traveling and in the home city" picture="food.jpg" value="5"/>
&lt!--- some more other stuff -->

After

&lt!--- some other stuff -->
<goods type="goods" name="food" tooltip="Used for traveling and in the home city" picture="food.jpg" value="5"/>
<goods type="goods" name="coal" tooltip="do something" picture="coal.jpg" value="25"/>
&lt!--- some more other stuff -->

The designer want to be able to go into the xml document and add a new goods without being forced to edit the code as well. But I have no clue how to do this or even how to think about it to solve it.

Anyone here that has an idea how this can be achived?