Don't use Excel?
One of the beautiful things about Notes is that Lotus/IBM doesn't decide to change your data for you.
One of the many many issues with Microsoft products is that they think they know more than everyone else, and just change your data with no warning. excel is literally the worst product ever.
One workaround i've found over the years, is to write text data in Quotes, so that a given line in your text file might look like:
"column 1 text","456789098765","more text",12345,67890,"xxxx"
Excel should then read the value as text, not a number.