There's a plugin called SEO Ultimate that automatically inserts a linkbox with the html code in it for the link. The code is directly editable in the plugin options and should be easy to modify for what you want. It looks like this by default:
Code:
<div class="su-linkbox" id="post-{id}-linkbox"><div class="su-linkbox-label">
Link to this post!</div>
<div class="su-linkbox-field">
<input type="text" value="<a href="{url}">{title}</a>" onclick="javascript:this.select()" readonly="readonly" style="width: 100%;" />
</div></div>
I imagine you could just replace the <a href= stuff with bbcode stuff but I'm no coder so I don't really know.