I want to create a table (by "table" I just mean a bunch of columns of
numbers and formulas laid side by side, I don't know whether "table" has a
more technical meaning) where I manually enter a column of numbers, and
update those numbers periodically. The table is of fixed size.

I would like to create another table (on the same worksheet) that will
record the history of one column of the first table, the column that I will
be manually entering. For example, the first column of this second table
will permanently record the values that the first column of the first table
had on September 15, the second column of the second table will permanently
record the values that the first column of the first table had on September
16, and so on. This second table will grow wider over time. Do I have to
enter the numbers manually into the second table even after I have manually
entered them into the first table, or is there a way to use formulas so that
the numbers will automatically be entered into the second table? My concern
is that if I use formulas then every column of the second table will change
every time I enter updated numbers in the first table. I don't want every
column to change, I just want to add a new column with the latest numbers
while preserving the previous values of these numbers in the other columns.

What might be a big help is if there were a way to turn a formula
permanently into the constant number that it has calculated at a point in
time. For example, if the formula in cell a10 is "=a1" and the current value
of cell a1 is 42, is there a way to change cell a10 so that it will
permanently record 42 and no longer be dependent on cell a1. (Of course, I
would like to do this without having to erase the formula in cell a10 and
manually enter 42 into cell a10, though this would work if there were no
alternative.)