Having upgraded PC, changed to Win10 and reinstalled Office 2013, I find a problem with one of my files (that used to work OK in Win7) - when I try to save, it says Excel has run out of resources and cannot evaluate my formulas. I am aware that it may be because I'm running Excel 32-bit not 64-bit - but it doesn't seem to come anywhere near the 2GB memory limit, and I now see the problem even when I simplify the spreadsheet to around 5 lines, 30 cells - so I think it's more likely to be the limit on 64 nested functions or something similar.

Unfortunately, and weirdly, the same simplified spreadsheet sometimes works fine (without me changing anything). It seems there's something internal in Excel which flips and allows the recalculation to work. I've tested 50 different versions, and the results are always inconsistent.

Anyway, having given the background, maybe someone can give some general advice on simplifying the structure of my spreadsheet, as I know it's overly complex. The structure of each line will have content like this (an example of just a few cells from row 263 - the whole thing is replicated across a few hundred rows, maybe a dozen sheets, also cross-referenced):

There must be an easier way of doing this than having multiple IF()s in each cell, e.g. via Functions, Macros, Arrays or something, but I'm not sure of the best way to proceed... Advice welcome!