您需要使用观察者创建新的扩展名.

You need to create a new extension with observer.

对于实例，我创建了扩展Jakkor_Setstore.因此文件夹看起来像这样:

For Instance I created extension Jakkor_Setstore. So the folders looked like this:

app/code/local/Jakkor
app/code/local/Jakkor/Setstore
app/code/local/Jakkor/Setstore/etc
app/code/local/Jakkor/Setstore/Model

在其他地方，有一个文件"config.xml":

In etc there was a file "config.xml":

<?xml version="1.0"?>
<config>
    <global>
        <models>
            <setstoreobserver>
                  <class>Setstore_Model</class>
           </setstoreobserver>
        </models>
     </global>
     <frontend>
        <events>
            <controller_action_predispatch>
                <observers>
                    <jakkor_setstore_model_observer>
                        <type>singleton</type>
                        <class>Jakkor_Setstore_Model_Observer</class>
                        <method>setstore</method>
                    </jakkor_setstore_model_observer>
                </observers>
            </controller_action_predispatch>
       </events>
    </frontend>
</config>

在Model中，有一个文件"Observer.php":

In Model there is a file "Observer.php":

class Jakkor_Setstore_Model_Observer extends Varien_Event_Observer
{
  public function setstore($observer)
  {
      if(Mage::getSingleton('customer/session')->isLoggedIn())
      {
        $groupId = Mage::getSingleton('customer/session')->getCustomerGroupId(); //get the group id
        if($groupId == 2) //I don't know what id has your reseller group, so 2 is an example, you need to set here the specific group
        {
          Mage::app()->setCurrentStore(2); //Set id of the store view without vat
        }
        else {
          Mage::app()->setCurrentStore(1); //set the store view with vat
        }
      }
  }
}

当然在app/etc/modules"Jakkor_Setstore.xml"中:

And of course in app/etc/modules "Jakkor_Setstore.xml":

<?xml version="1.0"?>
<config>
    <modules>
        <Jakkor_Setstore>
            <active>true</active>
            <codePool>local</codePool>
        </Jakkor_Setstore>
    </modules>
</config>

这已经过测试，并且可以正常工作.对不起，一团糟.我没有测试第一种方法.我认为应该可以.

This was tested and it is working. Sorry for the mess before. I didn't test the first approach. I thought that it should work.