Dear Paula,
relevant for the calculation of the dividend is the CALCULATION date from the
condition detail which can be different from the due date.
The position available at this date (again: the calculation date, not the
position date of the deal(s) is the relevant one) will be the basis for
calculation.
This means that you could try to fulfill your requirement by setting the calculation dates both of the condition and the deal(s) accordingly.
Best regards,
Marie