As far as I'm aware, this isn't possible due to the ridiculous way the Excel driver types each column.
If you must work with Excel, I'd probably change those template rows to force it to be a string rather than numeric (or use the IMEX=1 parameter in the connection string, to force it to always be text), then convert to a numeric in the data flow, so you have control over what to do in the event of receiving non-numeric data.