Once you complete the union 2 fields are added - Sheet and Table
the table will have 2 values - one for each of the unioned files - they will be they same but the second will have an integer appended
you can then conditional statements based on the table name i.e. order number = if [table name] = 'Table1' then [no.] else null end
you may need additional steps to complete your analysis not being able to see the data is a detriment
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