Power Query Table Select Rows

Hi,

Workbook with attempts attached.

I've been trying to sum the last 3 values based on dates for each customer, , but rather than grouping I'd like to use Table.SelectRows;

I've got

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This returns a column of tables of each customer, withing this I'd like to restrict this to only the last / max 3 dates.

I've got as far as

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but the last clause is seeing all the dates, I did think of using

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or A Source [Date] ,
but no good,
Any Suggestions,

Richard