How To Create A Cumulative Column Based Upon Another Column

I have a model built that calculates the daily Profit and loss ('Data for Pivot' tab, column M). I would like to calculate the cumulative profit and loss and am having a difficult time doing this with a simple formula. The Daily P/L column is empty (#NA value is in the cells) up until cell C138 as there is no data before that (which is the way it is supposed to be). However, once data has begun to be populated the daily profit and loss is shown (in this case from M138 onwards). The issue I am having is that I cannot seem to be able to create a formula that will capture the cumulative P/L. My desired result is evident in cells N179 onwards, as it simply captures the cumulative p/l. However, this only works if I change the formula once data is populated (in this case cell N177 is where i put in a new formula; the previous formula can be seen in cells N3-N176). If I attempt to put in the formula that is in cell N177 for all of the cells in column N, it gives me an error. Thus, I think that this may need to be programmed via VBA, but I have not been successful in doing this. The issue is that the data population in this model begins on different cells based on the different inputs that I put in ('Mov_Avg_Chart' tab, cells c6 and c8). Thus, I can't hard-code a formula based on a particular cell. If anyone can help me with this,