Crystal Reports Selecting records

Message

   I, like others I've seen, have been given Crystal Reports 11 and been thrown to the wolves learning how to use it.

I can get to the database I want, extract data from it, but need help in selecting certain records.

I deal with part numbers.  I want to select only the part numbers with the highest revision level.  My revisions range from 001 to possibly ZZZ.

When I run my basic report, the data (simplified) looks like this:

PART NUMBER     DESCRIPTION    REVISION      VENDOR

2100-01              gizmo                  001              ACME

2100-01              gizmo                  A00              ACME

2100-01              gizmo                  A00               AJAX              

2100-05             gizmo 3                 100               JUNO
2100-05             gizmo 3                 A00              BARKLEY

What I need in the report is only the two A00 revision occurences for PN 2100-01 and only the single A00 revision of PN 2100-05.

I've read some about subreports, but what is the best way to filter for the latest revisions?  I've tried MAX values, but Xtal reports comes back and says something to the effect the data has be extracted before it can find the max values (understandable).

Can I be helped?

Thanks, 

Dave