I am currently working on a report that displays orders that are marked in a group that is no longer active. In our system it is possible for a group to be listed twice if you have been a part and then are no longer a part of the group for auditing purposes. the records are told apart by a sequence number. I am looking for a way to make sure that crystal always selects the higher sequence number for the group associated, but get a message saying the function can not be calculated at this time when using IF(Maximum()<>1 in the selection formula any suggestions?

data is stored in the folowing
userid   Groupid seq   startdate    enddate
2545       dar     1      5/25/2012   7/20/2012
2545       dar     2      8/1/2012    null
2545       mdc     1      2/2/2011    null

and so on. I am linked to the table using userid and group id. if an end date is null then its the active group