case insensitivity

Hello every one.
 i want to use xsl:if for testing some string but discarding the case
sensitivity.
the sample is
    <xsl:when test="F2 = 'Starting Balance' ">
        <xsl:value-of select="F2"/>
     </fo:inline>
now i want to check it for lower case or upper case. I've already gone
through many codes but cannot understand its working. lower-case of xpath is
also not working.
Thanks
Regards,
Saqib javed