Excel Interop: Grouping columns - c++

Question

How do i group columns using Excel interop?
if i record a macro (usually a good way to get started) i get this code:
Columns("I:M").Select
Selection.Columns.Group
unfortunately this doesn't work due to several problems, at least in C++. First of all, Application.Selection returns a normal Range, then Range.Columns is another Range. And Range.Group is this method:
http://msdn.microsoft.com/en-us/library/microsoft.office.interop.excel.range.group%28v=office.11%29.aspx
This method only works in connection with pivot tables.
So how do i create a column group using Excel interop?
Even if i manage to create a group, how can i shrink/expand it? By that i mean clicking on the + to show the content of the group, or rather the other way around, "click" on the minus to hide the group. If i do that while recording a macro, it is not reflected in the macro at all.

Answer 1

Despite the fact that the Range.Group() documentation appears to relate to pivot tables, if you extract the columns using Range.Columns, and then apply the .Group() method to that range, it will have the desired effect. In C#:
Range range = sheet.get_Range("c1","e1");
range.Columns.Group();
Edit: The complete example, again in C# (apologies, it's the example I have handy):
Microsoft.Office.Interop.Excel.Application app = new Microsoft.Office.Interop.Excel.Application();
app.Visible = true;
app.Workbooks.Add();
Worksheet sheet = app.Workbooks[1].Sheets[1];
Range range = sheet.get_Range("c1","e1");
range.Columns.Group();

Answer 2

One thing the macro recorder obscures is the need to use the Range.EntireColumn property. Here's some code that groups, expands and collapses. I got this by googling and fooling around, but I think it gets the concepts right. Hopefully it's easy to translate into C++:
Sub test()
Dim ws As Excel.Worksheet
Set ws = ActiveSheet
With ws
If .Columns.OutlineLevel > 1 Then
'clear any existing hidden grouped columns and grouping
.Outline.ShowLevels columnlevels:=.Columns.OutlineLevel
.Range("1:1").EntireColumn.Ungroup
End If
'group
.Range("A:C").EntireColumn.Group
'collapse
ws.Outline.ShowLevels columnlevels:=1
'expand
ws.Outline.ShowLevels columnlevels:=.Columns.OutlineLevel
End With
End Sub