Use the Def property to specify a common value for given properties for all cells in the column. For instance, you can use the Def property to assign check boxes to all cells in the column, without enumerating them.

The following VB sample assigns checkboxes for all cells in the first column: 

ComboBox1.Columns(0).Def(exCellHasCheckBox) = True

The following VB sample changes the background color for all cells in the first column:

With ComboBox1.Columns(0)
    .Def(exCellBackColor) = RGB(240, 240, 240)
End With

The following C++ sample assigns checkboxes for all cells in the first column: 

COleVariant vtCheckBox( VARIANT_TRUE );
m_combobox.GetColumns().GetItem( COleVariant( (long) 0 ) ).SetDef( /*exCellHasCheckBox*/ 0, vtCheckBox );

The following C++ sample changes the background color for all cells in the first column:

COleVariant vtBackColor( (long)RGB(240, 240, 240) );
m_combobox.GetColumns().GetItem( COleVariant( (long) 0 ) ).SetDef( /*exCellBackColor*/ 4, vtBackColor );

The following VB.NET sample assigns checkboxes for all cells in the first column: 

With AxComboBox1.Columns(0)
    .Def(EXCOMBOBOXLib.DefColumnEnum.exCellHasCheckBox) = True
End With

The following VB.NET sample changes the background color for all cells in the first column:

With AxComboBox1.Columns(0)
    .Def(EXCOMBOBOXLib.DefColumnEnum.exCellBackColor) = ToUInt32(Color.WhiteSmoke)
End With

where the ToUInt32 function converts a Color expression to an OLE_COLOR, 

Shared Function ToUInt32(ByVal c As Color) As UInt32
    Dim i As Long
    i = c.R
    i = i + 256 * c.G
    i = i + 256 * 256 * c.B
    ToUInt32 = Convert.ToUInt32(i)
End Function

The following C# sample assigns checkboxes for all cells in the first column: 

axComboBox1.Columns[0].set_Def( EXCOMBOBOXLib.DefColumnEnum.exCellHasCheckBox, true );

The following C# sample changes the background color for all cells in the first column:

axComboBox1.Columns[0].set_Def(EXCOMBOBOXLib.DefColumnEnum.exCellBackColor, ToUInt32(Color.WhiteSmoke));

where the ToUInt32 function converts a Color expression to an OLE_COLOR, 

private UInt32 ToUInt32(Color c)
{
	long i;
	i = c.R;
	i = i + 256 * c.G;
	i = i + 256 * 256 * c.B;
	return Convert.ToUInt32(i);
}

The following VFP sample assigns checkboxes for all cells in the first column:

with thisform.ComboBox1.Columns(0)
	.Def( 0 ) = .t.
endwith

The following VFP sample changes the background color for all cells in the first column:

with thisform.ComboBox1.Columns(0)
	.Def( 4 ) = RGB(240, 240, 240)
endwith