Power Pivot DAX running total by Months

Hi,
is there a way to get a PP measure for a running total to recognize Month names, I've done this using field options,
and have attached a worksheet showing this but would like to achieve the same with a measure if possible,
I've tried this in power bi, and that does recognize the date Month names, so a matrix with Jan to Dec will give a running total if one is dropped in even if it's working off the actual date, but I don't think bi dates are the same as excel, in this case it seem they work better, in other cases, sorting, not as good.
So, in the first pivot table I'd like to write a measure that gives the same as the field settings

Richard.

Well thats a novel way round it, didn't bother with the Month Index , just used the date so;

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and it seems to work fine when the dates are removed and it's just months.
I'm not sure it's the ideal way of solving it re efficiency but it certainly works and no one else has come up with and answer.

Thanks,


RD