dynamic variable name/implementation question

Hi-
I'm trying to find a workaround or alternate implementation for a
particular problem I'm tring to solve.  I have various parameters that
are passed into the processor, and I would like to use their values in
the stylesheet.  However, I've found that XSLT 1.0 does not support
dynamic variables.
I would like to do the following:

XML:
...
<text-block>
   this is some text. Folowing is dynamic- <external-value
parameter="someParam"/> -preceding was dynamic
</text-block>
...

XSL:
...
<xsl:template match="external-vaue">
    <xsl:value-of select="$@parameter"/> <!-- this won't work -->
</xsl:template>
...

where there is a parameter "someParam" passed into the stylesheet - say
someParam="foo".  My output would be:
...
 this is some text. Folowing is dynamic- foo -preceding was dynamic
...

Has anybody else ever needed this fuctionality?