Crystal Crosstab need help adding columns to highlight average and difference

I have a crosstab which shows a count of a callid for this month and previous month by customer id this is showing a top 10 group. My problem is I need to have a column that shows the difference between this month and previous month and then I need a column for the 12 month average

i.e. My crosstab currently looks like this

                             Sept        Aug
Customer1                     80         20
Customer2                     56         58
Customer3                     60         88
Customer4                     71         54
Customer5                     98         45

I need it to look like this

                            Sept        Aug       Difference     12mthAvg
Customer1                     80         20        60              65
Customer2                     56         58        -2              73
Customer3                     60         88      开发者_如何学JAVA -28              52
Customer4                     71         54        17              48
Customer5                     98         45        53              56

Is this possible?

Thanks,

Annette

The monthly average is easy. Right click the first row in the 'Total' column (by default, this is the left-most column), select 'Edit Summary...', and choose 'Average' from the 'Calculate this summary' combo-box. This assumes that the cross-tab always includes 12 months of data, which can be easily done by setting an appropriate record-selection formula.

I'll do some research on the monthly deltas and post my results.

** edit **

If you have Crystal Reports 2008, you can add a calculated column. You will need to have 11 of these.

Here are the steps:

1. Select the second column's header and choose Calculated Member | Insert Column.
2. Right click the first cell in the new column and select Calculated Member | Edit Calculation Formula

3. Enter the following in the formula's text:

   //find the difference in values of the current row in the two columns to the left of the //current (calculated) column GridValueAt(CurrentRowIndex,CurrentColumnIndex-1,CurrentSummaryIndex) + GridValueAt(CurrentrowIndex,CurrentColumnIndex-2,CurrentSummaryIndex)

4. Change the column header's text by right clicking the header and choosing Calculated Member | Edit Header Formula'.

5. Repeat steps 1-4 for each calculated column. In step 3, change the offset from -2 to -3 to account for the presence of the calculated column.