crosstab help

Hi All,

I have a cross tab report having columns as brand and rows as location.

For every  Brand I have summary fields like sales,cost,variance.

It is like this

                                 B1                                                         B2                                      B3

Loc1               sales        Cost       Var                      sales        Cost       Var              sales        Cost       Var     

Now I need change the background color of   sales        Cost       Var    headers  alternately.

Please help