Adjusting sorted list

I have the following XML:
<a>
    <b>4</b>
    <b>9</b>
    <b>6</b>
    <b>1</b>
    <b>8</b>
    <b>6</b>
    <b>4</b>
    <b>7</b>
</a>

I am trying to generate the following ouput:
<a>
    <b rank="1">1</b>
    <b rank="2">4</b>
    <b rank="2">4</b>
    <b rank="3">6</b>
    <b rank="3">6</b>
    <b rank="4">7</b>
    <b rank="5">8</b>
    <b rank="6">9</b>
</a>

Using xsl:for-each with a sort on b and then using position() I can get
a ranking from 1 to 8 but I have no idea how to achieve the above.

I have dug around in the archives for some ideas but to no avail.
I see that I can't use a variable and adjust it's value with each
iteration (as it's not actually iterating).
I have also looked into using a recursive named template but am not sure
how to achieve the above and sort the output???

Thanks in advance for any help.

Andrew


 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list