public void Split(
    bool isColumn,
    Predicate<FieldValueCell> match,
    bool firstCellOnly,
    IList<FieldValueSplitData> cells
)

Public Sub Split(
    isColumn As Boolean,
    match As Predicate(Of FieldValueCell),
    firstCellOnly As Boolean,
    cells As IList(Of FieldValueSplitData)
)

<Window xmlns:dxpg="http://schemas.devexpress.com/winfx/2008/xaml/pivotgrid" 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
        xmlns:dx="http://schemas.devexpress.com/winfx/2008/xaml/core" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        x:Class="DXPivotGrid_SplittingCells.Window1" 
        dx:ThemeManager.ThemeName="LightGray" 
        Height="580" Width="1200"
        Loaded="Window_Loaded"
        Title="Window1">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <dxpg:PivotGridControl Grid.Row="1" Margin="2,2,2,0" Name="pivotGrid" AllowDrag="False"
                               FieldValueDisplayText="pivotGrid_FieldValueDisplayText" 
                               AllowFilter="False" DataProcessingEngine="Optimized"/>
        <GroupBox Grid.Row="0" Height="Auto" Margin="2,2,2,0"
                  Name="groupBox1" VerticalAlignment="Bottom">
            <StackPanel Orientation="Vertical">
                <RadioButton x:Name="rbDefault" IsChecked="True" Content="Default Layout"
                             Margin="0,0,0,2" Checked="rbDefault_Checked"/>
                <RadioButton Checked="rbDefault_Checked" Margin="0,2,0,0"
                             Content="Split Grand Total Column Header"/>
            </StackPanel>
        </GroupBox>
    </Grid>
</Window>

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Windows;
using DevExpress.Xpf.PivotGrid;
using DevExpress.XtraPivotGrid.Data;

namespace DXPivotGrid_SplittingCells {
    public partial class Window1 : Window {
        public Window1() {
            InitializeComponent();
            pivotGrid.CustomFieldValueCells += 
                new PivotCustomFieldValueCellsEventHandler(pivotGrid_CustomFieldValueCells);
        }
        void Window_Loaded(object sender, RoutedEventArgs e) {
            PivotHelper.FillPivot(pivotGrid);
            pivotGrid.DataSource = PivotHelper.GetDataTable();
            pivotGrid.BestFit();
        }
        void pivotGrid_CustomFieldValueCells(object sender, PivotCustomFieldValueCellsEventArgs e) {
            if (pivotGrid.DataSource == null) return;
            if (rbDefault.IsChecked == true) return;

            // Creates a predicate that returns true for the Grand Total
            // headers, and false for any other column/row header.
            // Only cells that match this predicate are split.
            Predicate<FieldValueCell> condition =
                new Predicate<FieldValueCell>(delegate(FieldValueCell matchCell) {
                return matchCell.ValueType == FieldValueType.GrandTotal &&
                    matchCell.Field == null;
            });

            // Creates a list of cell definitions that represent newly created cells.
            // Two definitions are added to the list. The first one identifies
            // the Price cell, which has two nested cells (the Retail Price and Wholesale Price
            // data field headers). The second one identifies the Count cell with 
            // one nested cell (the Quantity data field header).
            List<FieldValueSplitData> cells = new List<FieldValueSplitData>(2);
            cells.Add(new FieldValueSplitData("Price", 2));
            cells.Add(new FieldValueSplitData("Count", 1));

            // Performs splitting.
            e.Split(true, condition, cells);
        }
        void pivotGrid_FieldValueDisplayText(object sender, PivotFieldDisplayTextEventArgs e) {
            if(e.Field == pivotGrid.Fields[PivotHelper.Month]) {
                e.DisplayText = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName((int)e.Value);
            }
        }
        private void rbDefault_Checked(object sender, RoutedEventArgs e) {
            pivotGrid.LayoutChanged();
        }
    }
}

Imports System
Imports System.Collections.Generic
Imports System.Globalization
Imports System.Windows
Imports DevExpress.Xpf.PivotGrid
Imports DevExpress.XtraPivotGrid.Data

Namespace DXPivotGrid_SplittingCells

    Public Partial Class Window1
        Inherits Window

        Public Sub New()
            Me.InitializeComponent()
            AddHandler Me.pivotGrid.CustomFieldValueCells, New PivotCustomFieldValueCellsEventHandler(AddressOf pivotGrid_CustomFieldValueCells)
        End Sub

        Private Sub Window_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
            PivotHelper.FillPivot(Me.pivotGrid)
            Me.pivotGrid.DataSource = GetDataTable()
            Me.pivotGrid.BestFit()
        End Sub

        Private Sub pivotGrid_CustomFieldValueCells(ByVal sender As Object, ByVal e As PivotCustomFieldValueCellsEventArgs)
            If Me.pivotGrid.DataSource Is Nothing Then Return
            If Me.rbDefault.IsChecked = True Then Return
            ' Creates a predicate that returns true for the Grand Total
            ' headers, and false for any other column/row header.
            ' Only cells that match this predicate are split.
            Dim condition As Predicate(Of FieldValueCell) = New Predicate(Of FieldValueCell)(Function(ByVal matchCell) matchCell.ValueType = FieldValueType.GrandTotal AndAlso matchCell.Field Is Nothing)
            ' Creates a list of cell definitions that represent newly created cells.
            ' Two definitions are added to the list. The first one identifies
            ' the Price cell, which has two nested cells (the Retail Price and Wholesale Price
            ' data field headers). The second one identifies the Count cell with 
            ' one nested cell (the Quantity data field header).
            Dim cells As List(Of FieldValueSplitData) = New List(Of FieldValueSplitData)(2)
            cells.Add(New FieldValueSplitData("Price", 2))
            cells.Add(New FieldValueSplitData("Count", 1))
            ' Performs splitting.
            e.Split(True, condition, cells)
        End Sub

        Private Sub pivotGrid_FieldValueDisplayText(ByVal sender As Object, ByVal e As PivotFieldDisplayTextEventArgs)
            If e.Field Is Me.pivotGrid.Fields(Month) Then
                e.DisplayText = CultureInfo.CurrentCulture.DateTimeFormat.GetMonthName(CInt(e.Value))
            End If
        End Sub

        Private Sub rbDefault_Checked(ByVal sender As Object, ByVal e As RoutedEventArgs)
            Me.pivotGrid.LayoutChanged()
        End Sub
    End Class
End Namespace