Alternate row color for matrix where i have Row group and colum group

Hi,

I am using matrix in my report which is having one Row Group called ROW_GROUP and one colum group called COLUMN_GROUP. i need to give alternate color for row. I am using this expression "IIf(RUNNINGVALUE(Fields!ROW_GROUP_COLUMN.Value,CountDistinct,Nothing)MOD 2,"White","#f6fb72")" but it is not working out. please anyone can help me on this issue.