If you're sure that it's always the first column that you'll use in a WHERE clause, then that will work too. The only thing is that performance will not be ideal, but that isn't much of a problem if your Excel files aren't too big.
BTW In the FOR loop, add a DROP Table DATA; statement after the LET vFile... line or you may be joining all columns from all Excel files into a single DATA table. I'm assuming that the autoconcatenate that will happen on your DATA2 table is intended?
If you can detect the correct name of the column-to-be-used in the WHERE clause from the actual filename in $(vFile), you could set a second variable e.g. vColumn to the name of the correct column to use. For example: