if you are not using any product options, you could pass only the ID as a querystring variable to standard cart display page. And add an if statement.
So the link would look like:
ItemUpdate.php?id=2
and in the cart display code, change the while loop:
<?php
while (!$eCart1->EOF()) {
?>
<tr>
<td class="eC_GroupColumn"><img src="<?php echo $eCart1->DisplayInfo("Thumbnail"); ?>" alt="Product thumbnail" class="eC_ProductThumb" />
<p class="eC_ItemName"><?php echo $eCart1->DisplayInfo("Name"); ?></p>
<p class="eC_ItemDescription">Description: <?php echo $eCart1->DisplayInfo("Description"); ?></p></td>
<td class="eC_PriceItem"><?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->DisplayInfo("Price")); ?></td>
<td class="eC_FormItem"><input type="text" name="eCart1_Quantity_<?php echo $eCart1->DisplayIndex; ?>" size="3" value="<?php echo $eCart1->DisplayInfo("Quantity"); ?>" /></td>
<td class="eC_FormItem"><input type="checkbox" value="<?php echo $eCart1->DisplayInfo("ID"); ?>" name="eCart1_Delete_<?php echo $eCart1->DisplayIndex; ?>" /></td>
<td class="eC_PriceItem"><?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->DisplayInfo("TotalPrice")); ?></td>
</tr>
<?php
$eCart1->MoveNext();
}
$eCart1->MoveFirst();
?>
add an if statement to compare the id querystring:
<?php
while (!$eCart1->EOF()) {
?>
<?php if(isset($_GET) && $_GET['id'] == DisplayInfo("ID")) { ?>
<tr>
<td class="eC_GroupColumn"><img src="<?php echo $eCart1->DisplayInfo("Thumbnail"); ?>" alt="Product thumbnail" class="eC_ProductThumb" />
<p class="eC_ItemName"><?php echo $eCart1->DisplayInfo("Name"); ?></p>
<p class="eC_ItemDescription">Description: <?php echo $eCart1->DisplayInfo("Description"); ?></p></td>
<td class="eC_PriceItem"><?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->DisplayInfo("Price")); ?></td>
<td class="eC_FormItem"><input type="text" name="eCart1_Quantity_<?php echo $eCart1->DisplayIndex; ?>" size="3" value="<?php echo $eCart1->DisplayInfo("Quantity"); ?>" /></td>
<td class="eC_FormItem"><input type="checkbox" value="<?php echo $eCart1->DisplayInfo("ID"); ?>" name="eCart1_Delete_<?php echo $eCart1->DisplayIndex; ?>" /></td>
<td class="eC_PriceItem"><?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->DisplayInfo("TotalPrice")); ?></td>
</tr>
<?php } ?>
<?php
$eCart1->MoveNext();
}
$eCart1->MoveFirst();
?>