Edwin,
Are you just trying to push some old studies in DCM4CHEE to another PACS in a one-time storage? If so, be sure you have the AE information stored in the archive, then use the toolkit to request a move (see
http://www.dcm4che.org/confluence/display/d2/dcmqr).
If you are trying to ensure that every study that get *stored* to DCM4CHEE gets forwarded to another PACS if it is older than a certain date, then use the forward.xsl tool. It will not forward studies that currently exist in the archive; only those that are stored after the forward.xsl is installed. Your forward.xsl does have some formatting issues. Try something like:
<xsl:variable name="studydate" select="normalize-space(attr[@tag='00080020'])" />
<xsl:choose>
<xsl:when test="$studydate>'20080101'">
<destination aet="NEW_PACS" />
</xsl:when>
</xsl:choose>
between your destinations tag.