Sort and select list values using xsl

what i want to do is to retreave the very first recurence of these values for eache SetCode

$<Root> $ $<Code>12</Code> $20140405 $</Set> $ $<Code>10</Code> $20140405 $</Set> $ $<Code>12</Code> $20140404 $</Set> $ $<Code>11</Code> $20140404 $</Set> $ $<Code>11</Code> $20140305 $</Set> $ $<Code>12</Code> $20140305 $</Set> $ $<Code>10</Code> $20140302 $</Set> $ `$

and what i want in result is :

i used foreach with sort by date,and position(), but dont get the right result

<Set>
    <Code>10</Code>
    <Date>20140405</Date>
    </Set>
    <Set>
    <Code>12</Code>
    <Date>20140404</Date>
    </Set>
    <Set>
    <Code>11</Code>
    <Date>20140404</Date>
    </Set>'
    `$
    :D