The DB Find Invoice form is accessed by clicking on the Find Invoice button on the DB Invoice form:
This form allows you to search for the relevant Invoice.
Add search criteria and click on the button. A Grid will be displayed at the bottom of the form displaying the Invoices that meet the search criteria:
Select a Invoice by clicking on the link in the Invoice No column:
You will be directed back to the DB Invoice form and the selected Invoice number will be added to the field.