XPath Expressions inside a variable

I am trying to build following element (which works):

<xsl:for-each select="document('mydoc.xml')/FirstSibling">
	<xsl:copy-of select="Row" />
</xsl:for-each>

I'm trying to parse a information to access a 2nd input document and path.
My input source (*.xml) looks like this:

<Portlet src="mydoc.xml" path="FirstSibling"/>

I tried:

<xsl:variable name="src" select="Portlet/@src" />
<xsl:variable name="path" select="Portlet/@path" />
<xsl:for-each select="document($src)/{$path}">
	<xsl:copy-of select="Row" />
</xsl:for-each>

But this doesn't work as it doesn't like the data type for $path.  How can I
accomplish my desired result?
Is it possible to do this with just one variable? or no variables?

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