You could make a Top 50% query with a field sorted in ascending order, and
another Top 50% query with the same field sorted in descending order (which
makes it in effect a Bottom 50% query). This second query (I will call it
qryBot50) will be in reverse order, so you will need either to base another
query on qryBot50 to reverse the order, or you will need to sort the
spreadsheet. There are other things you could do about the sorting, but
those are probably the simplest.
You could also use a number rather than a percent for the top half and
bottom half of the records. With either % or an actual number you open the
query in design view, click View > Properties, and look for the Top Values
line in the property sheet.
In any case, be sure to check for values that appear both at the bottom of
the top group of records and the top of the bottom group. There could be
overlap in some cases. There is no automatic "tie-breaker". Use File >
Export to send the data to spreadsheets.
