Thanks a lot, it now works fine.
I only edited file admin/invoice.php where
added there inside the select statement
of $order_check, the field customers_id .
Then below this statement added the code
Code:
$xinfocode = "SELECT customers_group_pricing
from " . TABLE_CUSTOMERS . "
where customers_id ='" . $order_check->fields['customers_id'] . "'";
$xinfo = $db->Execute($xinfocode);
Then further below where the print outs are, added
Code:
<tr>
<td class="main" style="color:#FF0000"><?php echo "Discount Group: "; ?>
<?php if($xinfo->fields['customers_group_pricing']== 2) echo "Wholesale (Group A)";
if($xinfo->fields['customers_group_pricing']== 1) echo "1";
if($xinfo->fields['customers_group_pricing']== 0) echo "Retail";?></td>
</tr>