Power Query Groupd and running total function

I've been trying t write a function to group and then perform running total on each group, the two functions work fine
independently but I can't get them in one hit, don't know if possible?

workbook attached

I've got as far as ;

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But the error says it cannot convert the grouped 'table' column to table, is this possible to do any suggestions.
I've attached workbook with attempts and working out.

Ri

thanks, I'll experiment, the reason i used 'text' for the second inner table was I want to use the column name, well you've probably seen what I did.
As to the output, rather than grouping and then using the running total I just wanted to see if it could be done in one. there are two or three videos,
but they're all; make function, group data and then use running total function.


Richard