Since the data is in two different records, there are several options that can access the date from the preceding record in order to subtract the two dates and get the elapsed time in days.
GetNthRecord can access the preceding record:
Define cPrevDate as:
IF ( Get ( RecordNumber ) > 1 ; GetNthRecord ( Datefield ; Get ( RecordNumber ) - 1 ) )
Define cElapsedDays as: IF ( NotIsEmpty ( cPrevDate ) ; DateField - cPrevDate )
But this isn't always practical. You may also want to set up a self join relationship that matches to the preceding record. Such a relationship can make it possible to either refer directly to the date field from the previous record in your calculation or you can use a date field with an auto-enter setting that copies the date from the preceding record so that you can compute the difference.
would it be possible to get demo sample from you ? as i can not do it after many attempts Phil