Growth rate (Month Over Month)

Hello all,

I want to make growth rates for Revenue Month over Month ( = percent change) for this table:

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So, I need to sum up values for all dates taking into account country and source, the sum up all values for all dates in the month, and finally calculate the percentage change.

The problem is that every date occurs 28 times, sice there are 14 countires and 2 sources. So, the solution could be -  previous month total appear ones (e.g. on the first day of month). Could you please help me with this?

I will be very grateful for your help!