If you just need a sum for all of them:
Create a date type parameter and select:
Allow Multiple Values
Range Values
Then place "{yourtable.yourfield} in {yourparameter}" in the record selection criteria.
If you want them summed separately for each range of values entered, then I have a weak solution.
I'll preface this with suggesting that this type of thing is better performed by a database.
Create a running total for however many ranges you think might exist at maximum, for each, add the column to sum, then place something akin to ths in the Evaluate->Use a Formula area:
//(Example for Running Total #1 field
if count({?some date}) > 0 then
{Orders.Order Date} >= minimum({?some date}[1])
and
{Orders.Order Date} <= maximum({?some date}[1])
else
False
Note that you use Crystal's array convention for the date range array itself (the [1]), and the min and max to select the ranges from within them. So you'd increment the > qty for the if and and the array subscript (the [1]) for each running total field you create.
You could do something similar using a loop and storing each value to a numbervar array, and while this might increase the elegance and get a nod and a wink from some coders, this example should suffice if there aren't so many ranges.
And there's probably a better way...
<shrug>
-k
kai@informeddatadecisions.com