How to compare a value in the current row with a value in the previous row?

Experts-

In my report, I want to report on the numeric difference between two values in order to show the delta. For example:

Month 1:  35 widgets   Delta: Unknown
Month 2:  15 widgets   Delta: -20
Month 3:  17 widgets   Delta: +2
Month 4:  22 widgets   Delta: +5

Can I create a formula in Crystal that will do this? (I suppose I need to store the previous row's widget count as a variable, so I can then compare it with the current row's count.) I also need to handle--as the example shows--the first row that won't have a previous row for comparison.

Thanks.
DataDesignITAsked:
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mlmccConnect With a Mentor Commented:
Try this

Name - MyDelta
Formula
If (PreviousIsNull({YourQuantityField})) then
  "Unknown"
Else
  ToText({YourQuantityField} - Previous({YourQuantityField}),0)

mlmcc
0
 
DataDesignITAuthor Commented:
Perfect! Just what I needed. Thanks.
0
 
mlmccCommented:
Glad i could help

mlmcc
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