Each month is a new file and individual to each other, meaning it I don't do nothing to the file other than copy paste and use 5 macros to control the whole data input/output.
Where there is a will there is a way to make it work, all it means is just a modification of formulas. But in doing so using data from other files is possible just depends on if it will work without errors to the new file system. Everything relies on each other in the file, when something doesn't work it all goes down. But that is the joys of having virtually 100% automation.
