<?php $customerSession = Mage::getSingleton('customer/session');
if($customerSession->isLoggedIn()){
      $groupId = $customerSession->getCustomerGroupId();
      $group = Mage::getModel('customer/group')->load($groupId);
      if ('Wholesale' == $group->getCode()){ //or $group->getCustomerGroupCode()
        foreach ($_product->getTypeInstance(true)->getUsedProducts ( null, $_product) as $simple) {
     $qty = Mage::getModel('cataloginventory/stock_item')->loadByProduct($simple)->getQty();
     echo $simple->getName()." with size ".$simple->getSize()." have a stock of $qty";
     echo '<br/>';
 }

    }
}?>