[xsl] help with testing for non-alphabetic values

["Zaneta Au" <zaneta.au@xxxxxxxxx>]

Hi,

I was wondering if there is anyway of testing for non-alphabetic values.
I know that I can test for numeric values using:

<xsl:if test="string(number(@value))='NaN'"/>

However, for what I'm doing, I need to include any symbols as well as 
numeric values, ie all non-alphabetic values. Is there any way of 
testing for this without having to go through the alphabet...

<xsl:if test="not(@value='a')"/>
  <xsl:if test="not(@value='b')"/>
     ....

Please help,

Thanks,

Zaneta