The CellWidth property specifies the cell's width. The CellWidth property has effect only if the cell contains inner cells. The SplitCell method splits a cell in two cells ( the newly created cell is called inner cell ). Use the InnerCell property to get the inner cell. Use the CellParent property to get the parent of the inner cell. Use the CellItem property to get the item that's the owner of the cell. Use the BeginUpdate and EndUpdate methods to refresh the cell's width when changing it on the fly.  

The CellWidth property specifies the width of the cell, where the cell is divided in two or multiple (inner) cells like follows:

• if the CellWidth property is less than zero, the master cell calculates the width of the inner cell, so all the inner cells with CellWidth less than zero have the same width in the master cell.
• if the CellWidth property is greater than zero, it indicates the width in pixels of the inner cell. 

By default, the CellWidth property is -1, and so when the user splits a cell the inner cell takes the right half of the area occupied by the master cell.

The following VB sample splits the first visible cell in three cells:

With Tree1
    .BeginUpdate
    .DrawGridLines = exAllLines
    With .Items
        Dim h As HITEM, f As HCELL
        h = .FirstVisibleItem
        f = .ItemCell(h, 0)
        f = .SplitCell(, f)
        .CellCaption(, f) = "Split 1"
        f = .SplitCell(, f)
        .CellCaption(, f) = "Split 2"
    End With
    .EndUpdate
End With

The following VB sample specifies that the inner cell should have 32 pixels:

With Tree1
    .BeginUpdate
    .DrawGridLines = exAllLines
    With .Items
        Dim h As HITEM, f As HCELL
        h = .FirstVisibleItem
        f = .ItemCell(h, 0)
        f = .SplitCell(, f)
        .CellCaption(, f) = "Split"
        .CellWidth(, f) = 32
    End With
    .EndUpdate
End With

The following VB sample adds an inner cell to the focused cell with 48 pixels width:

Tree1.BeginUpdate
With Tree1.Items
    Dim h As Long
    h = .SplitCell(.FocusItem, 0)
    .CellBackColor(, h) = vbBlack
    .CellForeColor(, h) = vbWhite
    .CellHAlignment(, h) = CenterAlignment
    .CellCaption(, h) = "inner"
    .CellWidth(, h) = 48
End With
Tree1.EndUpdate

The following C++ sample adds an inner cell to the focused cell with 48 pixels width:

#include "Items.h"
m_tree.BeginUpdate();
CItems items = m_tree.GetItems();
COleVariant vtItem( items.GetFocusItem() ), vtColumn( long(0) ), vtMissing; V_VT( &vtMissing ) = VT_ERROR;
COleVariant vtInner = items.GetSplitCell( vtItem, vtColumn );
items.SetCellWidth( vtMissing, vtInner, 48 );
items.SetCellBackColor( vtMissing, vtInner, 0 );
items.SetCellForeColor( vtMissing, vtInner, RGB(255,255,255) );
items.SetCellCaption( vtMissing, vtInner, COleVariant("inner") );
items.SetCellHAlignment( vtMissing, vtInner, 1 );
m_tree.EndUpdate();

The following VB.NET sample adds an inner cell to the focused cell with 48 pixels width:

With AxTree1
    .BeginUpdate()
    With .Items
        Dim iInner As Integer
        iInner = .SplitCell(.FocusItem, 0)
        .CellCaption(, iInner) = "inner"
        .CellHAlignment(, iInner) = EXTREELib.AlignmentEnum.CenterAlignment
        .CellWidth(, iInner) = 48
        .CellBackColor(, iInner) = 0
        .CellForeColor(, iInner) = ToUInt32(Color.White)
    End With
    .EndUpdate()
End With

The following C# sample adds an inner cell to the focused cell with 48 pixels width:

EXTREELib.Items items = axTree1.Items;
axTree1.BeginUpdate();
object iInner = items.get_SplitCell(axTree1.Items.FocusItem, 0);
items.set_CellCaption(null, iInner, "inner");
items.set_CellHAlignment(null, iInner, EXTREELib.AlignmentEnum.CenterAlignment);
items.set_CellBackColor(null, iInner, ToUInt32(Color.Black));
items.set_CellForeColor(null, iInner, ToUInt32(Color.White));
items.set_CellWidth(null, iInner, 48);
axTree1.EndUpdate();