need help with boolean comparison in XSL

Hello,

I have this comparison on my XSL page currently:

<xsl:when test="a:propstat/a:prop[office:EndDate !=
'']">

It is checking to see if the EndDate property exists.
My xml page is generated from properties (which are
sort of the equivalent of fields from a database) that
are pulled from a web storage system from Microsoft's
sharepoint portal server.

I need to check if an EndDate AND StartDate are equal
to each other but I'm not writing the correct syntax.
I tried this, and other iterations, but I receive an
error every time:

<xsl:when test="a:propstat/a:prop[office:EndDate =
a:propstat/a:prop[office:StartDate]]">

Can you please help with this?

Thank you

Sal


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