Indicate more than one record with matching fields - crystal-reports

Question

How can I indicate multiple records with the same Invoice number, but a different Sales Person ID? Our commissions can be split into multiple Salespeople, so there can be two different Salespeople per an invoice.
For example:
Grouped by: Sales Person ID (No Changing this option)
These records are in the Group Footer.
Sales Person ID: Invoice: Invoice Amt: Commissions: (Indicator)
4433 R100 20,000 3,025 * More than one record on the same invoice with a different sales person
4450 R096 1,987 320
4599 R100 20,000 3,025 * More than one record on the same invoice with a different sales person
4615 R148 560 75
4777 R122 2,574 356

Answer 1

If your report has less than 1000 invoices, you may try something like this.
This will return true when a second ocurrence of the invoice shows up. Then you can make something like set the row background do red.
Global NumberVar Array invoices;
numbervar nextIndex := count(invoices) + 1;
if nextIndex <= 1000 and not ({Result.InvoiceNumber} in invoices) then (
redim invoices [nextIndex];
invoices[nextIndex] := {Result.InvoiceNumber};
true;
)
else false;
If you want to detect the first occurrence, you will need something more sophisticated.

Answer 2

I think a SQL Expression Field would be a good way to achieve the result you want. You already have an InvoiceNo in each row of data. You just need a SQL Expression Field that uses that INvoiceNo to execute a query to count the number of salespersons who get a commission.
Something along the lines of:
(
Select Count(Sales_Person_Id)
From [Table]
Where [Table].InvoiceNo = InvoiceNo
)
This will return an integer value that represents the number of salespersons who are associated with one invoice. You can either drop the SQL Expression Field in your Indicator column, or write some other formula to do something special.