VS 2010 URL Rewrite Regex - Root Files Only

I am using url rewriting rules in my web.config and have it working but today I added a rule in a folder but my primary rule keeps overriding.

Web.config

Code:
<rewriter>
<rewrite url="~/folder/*_a_(.+).aspx" to="~/folder/index.aspx?id=$1" />
<rewrite url="~/*_a_(.+).aspx" to="~/listing.aspx?id=$1"/>
</rewriter>

Usage:

www.domain.com/topic_a_1.aspx -> This would load listing.aspx?id=1 which is great.

www.domain.com/folder/newtopc_a_2.aspx -> This is also loading listing.aspx?id=2 but should be loading index.aspx?id=2

I believe I need to change the second rule from *_a_... to something like [^/]_a_.... but that doesn't work.

What I can do so the second rule doesn't override my sub folder rules?