Query relating to transforming XML using XSL

Hi all,
I am new to XSL & I have 2 doubts.
1>
I have a XML file & using a XSL file I have to extract a portion of input XML(say SuperXML) to get a new XML(say subXML).The XSL file has to read a properties or CSV file to fetch some IDs & for each ID picked XSL has to transfrom super XML to generate subXML.Question, XSL is reading 2 files,properties/CSV & SuperXML,how can I do this.Is it possible that XSL reads 2 input files.I hope I m not confusing you.
2>
Now,a simple one

I have following skeleton of a XML file
<tag1>
..<tag2>
...<tag3>
...<catchme>first<catchme>
...<catchme>second<catchme>

& I want to get data from 2 <catchme> tags.I am using following in XSL but it is not getting data.Please advise where I m wrong.

Thanks in advance.
----------------------------------------------------------------------------

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl

utput method="xml" encoding="ISO-8859-1" indent="yes" />


<xsl:template match="/">
<tag1>
<xsl:apply-templates/>
</tag1>
</xsl:template>


<xsl:template match="tag1/tag2">
<tag2>
<xsl:apply-templates select="tag3"/>
</tag2>
</xsl:template>


<xsl:template match="tag1/tag2/tag3">
<tag3>
<xsl:for-each select="catchme">
<catchme><xsl:value-of select="catchme"/></catchme>
</xsl:for-each>
</tag3>
</xsl:template>

Rubal,
You can read the external xml files using document() function of xslt, check some xslt tutorials to learn the usage. www.w3schools.com tutorials were also good.