multi group level Percentages in crosstabs

[jambu]

I am using version 9 of crystal and would like to use crosstabs to show percentages in improvements at a number of group levels in my report.

The groups I have are

1 - All (xtab)
2 - Country (xtab)
3 - Region (xtab)
4 - Grade (Supressed) Can be any or all of A,B,C,D, E
Details (supressed) - Formulas that return 1 or 0 for OldGrade and NewGrade such that when one returns 1 the other returns 0.

I have a formula at group level 4 that does the following
if sum({@OldGrade})>0 then
(Sum({@NewGrade}) (% sum({@OldGrade}))-100 //Shows the percentage improvement
else
0

This is reported successfully at group level 3 (region) in the crosstab (along with the sums of the two detail level formulas per grade) but the two other crosstabs are reporting bizarre figures no matter what I set the summary operations to.

The question is how do I go about doing the same for level 2 and 1?
Should I create extra formulas at different group levels or are there crosstab summary operations that will do this?

I have been looking at this for a short while so it may just come to me as being blindingly obvious but I would appreciate any comments to help me along.
Note: the formula above is done from memory, the actual group level 3 crosstab/formula combination works.