**Refresh Unbound Subform problem**

[John M]

I am using a subform for data entry. After I enter book number the due date is calculated (see below)- this works fine. However the due date also depends on the total number of books. As this increases, the due date should be recalculated for the whole subform. This means that a person borrowing more books have a later due date to allow the borrow more time to read. How can I do this as the table is not based on any control source, I cannot requery it?

Thanks in advance