SSRS 2005 matrix query - Two levels of dynamic column group, but blanks in first level??

Hi all

My matrix in SSRS 2005 presents itself when I run the report as follows:

                                            Jan 2013                        Feb 2013                            Mar 2013
                                           Materials       Labour        Materials         Labour          Materials        Labour
Item 1                                 100               25              1524               236              258               354
Item 2                                 564               5408           870                84                55                 5485
Item 3                                 8405             848             8704              80                5405              84

Is there any way to make it display as follows:

                                            Jan 2013     Jan 2013     Feb 2013         Feb 2013       Mar 2013       Mar 2013
                                           Materials       Labour        Materials         Labour          Materials        Labour
Item 1                                 100               25              1524               236              258               354
Item 2                                 564               5408           870                84                55                 5485
Item 3                                 8405             848             8704              80                5405              84

I have been trying to fiddle with the report for ages but cannot figure this out. My matrix is set up as follows:

                                       Period     (ColumnGroup1)            Total
                                       CostType (ColumnGroup2)
Item (RowGroup1             Amount

Can anyone help with this please?
Many thanks
Naz