Crosstab Level 2 totals

abcd

I have 2 levels in the row area of a crosstab. Could somebody tell me please how to add totals in the Grand total area for the level 2 dimension?
ie.

Unit1 Group1
Group2
Unit1 total

Unit2 Group1
Group2
Unit2 total

Group1 total - ???
Group2 total - ???
Grand total

Thank you.