automatically incrementing a formula relating to an external workbook

Hi, This is my first post.

I am trying to automatically fill a cell, on the master sheet, with data from a cell in an external workbook.
My worksheet, Profit and Loss Invoice Test, contains columns for Material, Labour and Total. What I am trying to achieve is for these cells to be populated with an automatically incrementing formula, based on the Invoice Number. I have been manually linking each cell reference but it is a slow painful task.

When an Invoice is produced Material, Labour and Total are in cells D8, V29 and V31. They are linked to T10, U10 and Z10 in the Profit and Loss Invoice Test Workbook, Main Accouint. The workbook and invoices are stored on a Network Drive.

I have managed to automatically generate a hyperlink (M10) to access the Invoices, from my research of threads posted on the site, but have been unable to source an answer to this problem.

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