Thank you for your post.
Since your Invoice table is linked to your Suppliers table, create the report in the Suppliers table and reference the values in the Invoice table. For example, if the line item total in the Invoice table is named "Total Line Item", then create a calculation field "Total Invoices" with the formula: Sum (Invoice::Total Line Item)
If there are three portals, with three totals named "Total Line Item1", "Total Line Item2" and "Total Line Item3", then the formula would be:
Sum (Invoice::Total Line Item1) + Sum (Invoice::Total Line Item2) + Sum (Invoice::Total Line Item3)
You will then have an amount for each Supplier.
Please let me know if you need clarification for any of the above steps.
I have a table that is sorted by a "Case ID" field, I want to create a field that computes a running count(e.g. 1,2,3,4,etc) for the Case ID's and then restarts the count when a new set of Case ID's are in the field? I know I can create a summary field to do this, but the user would need to modify this field later and from what I've read a summary field can't be modified.