Moving total which uses two calculated fields and also uses its previous value

Hi folks I am new to Spotfire and having difficulty in replicating one of the formulas from Excel to spotfire.


the above is the formula I have in excel where B132 and subsequent columns are calculated by using the previous value and the current values in [Monthly impact on cash] and  [running total]

But the expected result is

[[{"fid":"127146","view_mode":"default","attributes":{"height":"84","width":"1530","class":"media-element file-default"},"fields":{"format":"default","field_file_image_alt_text[und][0][value]":"","field_file_image_title_text[und][0][value]":""},"type":"media"}]]

So although the results match till Oct as shown above they don't seem to match afterwards.

Please let me know what can I do to get the same values. Any help in deeply appreciated.