How to count the number of pages per supplier in a report using RTF.

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I am creating reports using BIP (BI Publisher), and I use RTF templates for the layout.
The report outputs data for multiple suppliers at once.
I want to count the number of pages per supplier.

Example:

• Supplier A: 3 pages
• Supplier B: 5 pages
• Supplier C: 4 pages
• Total: 12 pages

Pages 1 to 3 contain data for Supplier A.
I want the page numbers to be displayed as: 1/3, 2/3, 3/3

Pages 4 to 8 contain data for Supplier B.
I want the page numbers to be displayed as: 1/5, 2/5, 3/5, 4/5, 5/5

Pages 9 to 12 contain data for Supplier C.
I want the page numbers to be displayed as: