How to create a XML file with the default format

I'm beginner in XML and I have this informations

box1 -> name, colour, from

box2 -> name, weight

box3 -> name, colour, from, weight

and I want to make one XML file like this:

<boxName>name1
    <boxColour>colour1</boxColour>
    <boxFrom>from1</boxFrom>
</boxName>
<boxName>name2
    <boxColour>colour2</boxColour>
    <boxWeight>weight2</boxWeight>
</boxName>
<boxName>name3
    <boxColour>colour3</boxColour>
    <boxFrom>from3</boxFrom>
    <boxWeight>weight3</boxWeight>
</boxName>

I created my XML in this form:

TiXmlDocument doc;
TiXmlDeclaration* decl = new TiXmlDeclaration("1.0", "utf-8", "");
doc.LinkEndChild( decl );
TiXmlElement* element = new TiXmlElement("boxName");
doc.LinkEndChild(element);
TiXmlText* text = new TiXmlText("name1");
element->LinkEndChild(text);
TiXmlElement* element2 = new TiXmlElement("boxColour");
TiXmlElement* element3 = new TiXmlElement("boxFrom");
TiXmlText* text2 = new TiXmlText("colour1");
TiXmlText* text3 = new TiXmlText(from1);
element->LinkEndChild(element2);
element->LinkEndChild(element3);
element2->LinkEndChild(text2);
element3->LinkEndChild(text3);
doc.SaveFile( "XML.xml" );

but the problem is that number of boxes is unknown and each box my have 1,2,3 or more child, but the format for each box and it's information is the same (as the above)

please help me to make the XML file

Thanks