In a worksheet that I have been using for a few years I add daily rows of
data to 2 new columns each year (the data in the new columns get compared
against the data in the previous columns). One column (left column) is
numeric and the next column is datetime (so for several years we have a
numeric column followed by a datatime column and the following year is
Numeric column followed by a datetime column ...). This year the numeric
column keeps changing to datetime when I add a new piece of data to the cell
in the next row and I have to keep reformatting it to numeric. Why doesn't
this column stay in Numeric format?

Say the column with the problem is column X. Column Y is supposed to be
datetime. So I go to column Z which is not having this problem. I delete
the old X/Y columns so now Z is the new X column. But now this new column is
also having the problem. What is happening here? Is this worksheet
corrupted (I sure hope not becuase it would just be a pain to recreate -
with the legacy data and all).

Any suggestions appreciated.

Thanks,
Rich