Hello Richard, I am using Access 2013.  I am getting an error message when I choose the null value for both check boxes in the purchase order form. I thought maybe it was my code but i downloaded your database and it gives me the same error so i am thinking  it must be the version i am using vs the version that you used at the time.  What can I do to the code to fix this?  Here is the code that is highlighted in yellow when i click to debug:  
Private Sub PODetailUpdate()

    If IsNull(POList) Then
        ' no PO selected - show no records
        Me.RecordSource = "SELECT * FROM PurchaseOrderT WHERE PurchaseOrderID=-1"
        PurchaseOrderDetailsF.Form.RecordSource = _
            "SELECT * FROM PurchaseOrderDetailsT WHERE PurchaseOrderID=-1"

ALSO... The code i copy and pasted from above to get the inventory to update after receiving the items does not work.  I do not get any error messages ... but the inventory does not update...  Thanks for  your help!  Shallena

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Reply from Alex Hedley:

Does the sample db work on your machine?

There's a comment in the SI that explains the bug.
Bug in Access 329 Code
It's always useful to read the other student comments.