Array formula to return all steps of cumulative / running total

Hi all,

I'm scratching my head around an array formula that I'm trying to build. It has to be an array since I need to use it as an input for a function.

Bascially what I'm looking for is the equivalent of each step of a cumulative / running total but in array form. It's easiest explained with an example so an image and workbook is attached.

arraycml.PNG

What I am aiming for is col D "Array Cml" to have an identical output to col C "Cml Sales" using only col B "Sales".

Can anyone point me in the right direction?

Thanks