URL problems with xml

I've recently been getting to grips with xsl style sheets as part of a new job, but I am having a problem with one aspect of it.

Basically we're running a Network CRM in .aspx, with .xsl style sheets to pull information out of the database and display it on the page. Under the Network, copies of the same CRM run as child networks, in the url format:

http://*parenturl*/*childnetworkname*

I've been scripting relative links within the xsl's in the following format:

<a>
             <xsl:attribute name="href">
               http://<xsl:value-of select="@NetworkDomain"/>/events/article/default.aspx?objid=<xsl:value-of select="@ObjectID"/>
             </xsl:attribute>
             <xsl:value-of select="@ObjectTitle"/>
           </a>

Where *NetworkDomain* is the root url of the instance of the network an object is created in. However, there is some conflict of some of my pages. What I'd like to do is to replace the <xsl:value-of select="@NetworkDomain"/> part of the link with a reference to the the variable *fragnetworkurl* which is the root url for each instance of the network as stored ion the header for each page. I nearly got it earlier to day by replacing <xsl:value-of select="@NetworkDomain"/> with <xsl:value-of select="//fragnetworkurl" /> but that crashed the whole CRM big time. I'm sure I'm making a hell of a n00b of a mistake, but any help anyone could give would be greatly appreciated.