When creating business rules is there a way to specify that certain rules will only be enforced if the record in question is a new one and not just editing an existing one?



For example I want to do a check to make sure that the PO number isnt already in the system.. but that would only apply to adding new purchase orders and not editing existing ones.

Yes.  You will need to look at the RowState of the row.  It will look something like this:

If MyBO.CurrentDataTable(MyBo.CurrentRowIndex).RowState = Added Then
   '-- Put your test
End If