getMultiCellValueRef - Multidimensional reading of date from xls file.
XML request, sent by the client to the server
    <xtra sid="1">
       <data name="test2" function="getMultiCellValueRef">
                  <xls sheet="1" cellMin="A1" cellMax="B2"/>
cellMin is the first cell, that the value is to be read from. cellMax is the last cell, that the value is to be read from.
XML response of the server to the client
     <response action="xtra" errorCode="0" sid="10">
         <data name="testXLS" function="getMultiCellValueRef">
            <result state="ok">
                <xls sheet="1" cell="A1"><![CDATA[val1]]></xls>
                <xls sheet="1" cell="A2"><![CDATA[val2]]></xls>
                <xls sheet="1" cell="B1"><![CDATA[val3]]></xls>
                <xls sheet="1" cell="B2"><![CDATA[val4]]></xls>
Values of all the cells between cellMin and cellMax are returned to the client. The contents of the cells is returned in UTF-8.