I have a spreadsheet that multiple users access and update multiple times per
month. At the end of the month, I would like to know what the values of
certain cells were for ongoing reporting and graphing. The values I want to
know are percentages, sums, etc.

I was hoping someone could help with a macro that executed itself at the end
of the month or if the sheet has to be open for it to be executed, a macro
that automatically captures this data the first time it's opened in a new
month.

Is there a cell function that could do this? I tried using a if/then
formula that captured the value on a given date but as soon as that date
passed, the value did not freeze indefinetly.