XF 1.5 Modifying sibling node navigation

[MJ0730]

I'm trying to create a small nav bar that only shows the previous/next node, instead of the entire sibling list.

<div id="nextPage" class="newclass">
    <div class="anotherclass">
        <ol class="siblingNodes">
            <xen:foreach loop="$siblingNodes" value="$node">
                <li class="{xen:if '{$node.node_id} == {$page.node_id}', 'currentNode', 'siblingNode'}">
                    <a href="{xen:link {$node.routePrefix}, $node}" class="{xen:if '{$node.node_id} == {$page.node_id}', 'selected'}">
                        <span class="_depth1 depthPad">{$node.title}</span>
                    </a>       
                </li>
            </xen:foreach>
        </ol>
    </div>
</div>

What do I replace

<xen:foreach loop="$siblingNodes" value="$node">

with so it only shows the previous/successive sibling node?

Thanks.