XSLT add values across multiple elements

[Tovny]

I'm stuck with a simple problem in my XML/XSLTI can't really put a proper name on the problem, and therefore can't seem to find any solution.XML:\[code\]<root> <entry gid ="001"> <level_1> <target_value>50</target_value> </level_1> </entry> <entry gid ="001"> <level_1> <target_value>30</target_value> </level_1> </entry> <entry gid ="002"> <level_1> <target_value>40</target_value> </level_1> </entry> <entry gid ="002"> <level_1> <target_value>20</target_value> </level_1> </entry></root>\[/code\]XSL:\[code\]<xsl:for-each select="entry[@gid='001']"> <xsl:if test="level_1/target_value != ''"> <xsl:value-of select="sum(level_1/target_value)" /> </xsl:if></xsl:for-each>\[/code\]Result:5030Any help would be greatly appriciated!