Grouping Tree Cols

Hi,

I want to group certain columns within the columns in a <treecols> tag
Is that possible? If so, how?

What I really want to achieve, is something that looks like this:
                |          GROUP 1         |     GROUP 2    |
Name        |    Col1     |     Col 2    |    Col3   |   Col4
John          |      1        |        2       |      3     |     4
Matt          |      3        |          4     |      7     |     3

Right now I have:
Name        |    Col1     |     Col 2  |    Col3   |    Col4
John          |      1        |        2    |      3      |     4

Is there a way of achieving this?

Thanks,
AI