ApexRepeat.xml

<apex:repeat value="{!opportunities}" var="opp">
   <Row>
    <Cell ><Data ss:Type="String">{!opp.Name}</Data>
        <NamedCell ss:Name="Name_Column"/></Cell>
    <Cell ><Data ss:Type="String">{!opp.StageName}</Data>
        <NamedCell ss:Name="Stage_Column"/></Cell>
    <Cell ><Data ss:Type="Number">{!opp.Amount}</Data>
        <NamedCell ss:Name="Amount_Column"/></Cell>
    <Cell ss:StyleID="s75" ss:Formula="=IFERROR(RC[-1]/Total_Amount_Cell,0)"><Data
      ss:Type="Number"></Data>
        <NamedCell ss:Name="Percentage_of_Total_Column"/></Cell>
   </Row>
</apex:repeat>