Invoice Approval Status Table

Hi,

   Can anyone help me with my concern.

   I have to monitor how many invoices where process each time the invoice validation run.

   So the solution is that to query the invoices before and after the Invoice validation to see how many invoices was process and we must exclude the invoices which is already "Validated" .

   Problem is that we try to query invoices which has a status of Validated, Never Validated and Needs to Revalidated but the approval_status column was null.

   I try to searched on net and saw this scirpt. I tried to used it but still i get a null value.