using DevExpress.Xpf.PivotGrid;

if (!IsPostBack && !IsCallback) {
   // Gets a reference to the CategoryName field. 
   PivotGridField field = ASPxPivotGrid1.Fields["CategoryName"];
   ASPxPivotGrid1.BeginUpdate();
   try {
      // Clears the custom total collection. 
      field.CustomTotals.Clear();
      // Adds items to the custom total collection with  
      // the specified summary types. 
      field.CustomTotals.Add(PivotSummaryType.Sum);
      field.CustomTotals.Add(PivotSummaryType.Max);
      // Makes the custom totals visible for this field. 
      field.TotalsVisibility = PivotTotalsVisibility.CustomTotals; 
   }
   finally {
      ASPxPivotGrid1.EndUpdate();
   }
}

Imports using DevExpress.Xpf.PivotGrid

If (Not IsPostBack) AndAlso (Not IsCallback) Then
   ' Gets a reference to the CategoryName field. 
   Dim field As PivotGridField = ASPxPivotGrid1.Fields("CategoryName")
   ASPxPivotGrid1.BeginUpdate()
   Try 
      ' Clears the custom total collection. 
      field.CustomTotals.Clear()
      ' Adds items to the custom total collection with  
      ' the specified summary types. 
      field.CustomTotals.Add(PivotSummaryType.Sum)
      field.CustomTotals.Add(PivotSummaryType.Max)
      ' Makes the custom totals visible for this field. 
      field.TotalsVisibility = PivotTotalsVisibility.CustomTotals
   Finally 
      ASPxPivotGrid1.EndUpdate()
   End Try 
End If

<dx:ASPxPivotGrid ID="ASPxPivotGrid1" runat="server" ClientIDMode="AutoID" DataSourceID="SqlDataSource1">
    <Fields>
        <dx:PivotGridField ID="fieldCountry" Area="ColumnArea" AreaIndex="0" FieldName="Country" Name="fieldCountry">
        </dx:PivotGridField>
        <dx:PivotGridField ID="fieldProductName" Area="RowArea" AreaIndex="1" Caption="Product" FieldName="ProductName" Name="fieldProductName">
        </dx:PivotGridField>
        <dx:PivotGridField ID="fieldCategoryName" Area="RowArea" AreaIndex="0" Caption="Category" FieldName="CategoryName" 
            Name="fieldCategoryName" TotalsVisibility="CustomTotals">
            <CustomTotals>
                <dx:PivotGridCustomTotal SummaryType="Sum" />
                <dx:PivotGridCustomTotal SummaryType="Max" />
            </CustomTotals>
        </dx:PivotGridField>
        <dx:PivotGridField ID="fieldExtendedPrice" Area="DataArea" AreaIndex="0" Caption="Total Sum" FieldName="Extended_Price" Name="fieldExtendedPrice">
        </dx:PivotGridField>
    </Fields>
</dx:ASPxPivotGrid>