Style variable not working in Crosstab rows

[kris.nlr]

Folks,

I am using Cognos 8.3 for report development.

Issue: I am unable to apply style condition in Cross tab rows.

Example:
I have 2 data items A, B which is coming from model directly and I have created one calculated item i.e. C=A+B. I have created a string conditional variable with following conditions.

if([Main].[C]<=10)
then 'Green'
else if([Main].[C] between 10 and 20)
then 'Amber'
else if([Main].[C]>20)
then 'Red'
else 'NULL'

A       10       20     30      40
B       12       6        9        10
C       22       26     39       50

I no need to display 'C' in crosstab report but, if i remove C from crosstab, it is giving error that item C is not present in Legend, so i have kept the C in report and apply box type none property.

I want to apply this style variable condition on A and B, i.e. i need to change the Background color for rows A and B.

When i try to apply the style variable on row 'A' or 'B' it is going to NULL condition.

Is there any version issue with 8.3 that we cannot apply a calculated item style condition on Cross-tab rows (in this case A or B). But the same condition is working in List report and even Cognos 8.4.1 version.

Please let me know if there is any other way to solve this issue.

Thanks