Conditional formating based on two diferent fields values

Hello,

I have created a report on Report Builder 3.0 that has a structure similar to the following example

Event ID, Event Date, Participant ID, Event Class ....

1728 01/24/2012 1701 A23

01/25/2012 1042 A23

01/26/2012 1903 R15

2015 03/18/2012 2380 Z10

03/19/2012 2489 X44

03/20/2012 3012 Z10

In this query, the transactions are grouped by Event ID. An event could last many days and have many participants with unique Participant IDs. However, the one constant is that all transactions for the same event must be coded with the same Event Class. In our case, the Event Class code given to the first instance of an Event Date should dictate what the Event Class code should be coded as for the remaining transactions under the same Event ID.

In the above example (Event ID 1728) the last Event Class is different from the first (or earliest) entry under that same Event ID. The same is true for the second transaction on Event ID 2015.

I would like to know how to write an expression in the field color value that will create a conditional formatting to turn the Event Class red if any transaction posted after the first one for that event has a different Event Class value. In this example, both R15 and X44 are anomalies that should appear in red for us to correct them in the database.

Thank you so much for your assistance.

Regards,

Manuel