> But the problem is, there can be other <fontface> tags too, 
> in my future ones... I want this Path replacement ONLY to be 
> done only for <VisualObject> tags with attribute "CBarCode".
> 

Then write a more selective pattern:

<xsl:template match="VisualObject[@xsi:type='CBarCode']/fontface">

Or if your stylesheet is schema-aware:

<xsl:template match="element(VisualObject,CBarCode)/fontface">

Michael Kay
http://www.saxonica.com/