Increment on change?

[valkyry]

I have a query where it pulls the last ReceiptNumber from ReceiptHistory.

I was hoping someone can help me on how I can have the last ReceiptNumber increase by 1 on change of the PO Number.

Example: the last ReceiptNumber say is 12345
So in my query it says:
ReceiptNo: DMax("ReceiptNo","qryLastReceiptNumber") with PONumber and other data fields.

I need the query to show the ReceiptNo to be 12346 and so on each instance of a change in the PONumber.

hope that made sense?

 

[valkyry]

Here's the query result:
PONumber ReceiptNo
1001967 100191
1002005 100191

Need it to be:
PONumber ReceiptNo
1001967 100192
1002005 100193