Crystal Reports DataDate Field

Hello All:

In my Crystal Report, on refresh I would like to use a formula to capture the last DataDate value and pass it to my selection criteria. I tried the very simple

BeforeReadingRecords; DataDate

but DataDate apparently updates as soon as one clicks the Refresh button. So, my formula is capturing the DataDate value before reading records, but the DataDate field has at that point already updated to the current date. Is there any way I can force my formula to read the DataDate value when I click refresh, but before Crystal reads the current date?

Thanks,

Patrick