Crystal Reports Selecting Records

Message

I'm having trouble selecting the correct records. I'm trying to use Record Selection Formulas but I can't seem to get the 'Maximum' or 'NthLargest' to work. When I attempt to use either of these, I get 'a Boolean is required here' or ' ...this must be calculated later' errors.

The challenge is that I only want to return records when the
Maximum SequenceID is equal to ‘Networking’. An example of the data is shown below.

The AssignTable can hold multiple records for a given
MainID.

For any given MainID, there can be multiple SeqIDs and
GroupIDs.  The MainID is a primary key on
two other tables and I need to create a join query to pull matching records
from those other tables. 

MainID                 SequenceID       GroupID

2556                       4568789                Networking

2556                       4569589                Tech

2556                       4590001                Admin

2556                       4590252                Networking

2589                       4622589                HR

2589                       4632587                Networking

In the above scenario, I want to select these two records:
MainID                 SequenceID       GroupID
2556                4590252           Networking

2589                       4632587                Networking

These records should be selected because within a particular MainID, the Maximum (or 1thLargest) SequenceID  is equal to 'Networking'.

I was hoping to do this using the record selection formulas. If you think SQL is required, let me know.

Any and all suggestions are welcome.

Thank you.

Edited by tdavenport - 11 Jun 2009 at 8:11am