[~, ~, raw] = xlsread(somefile, 1);
[startrow, ~] = find(strncmpi(raw, 'AMPLITUDE', numel('AMPLITUDE')));
endrow = find(cellfun(@(x) ~isstr(x) && isnan(x), raw(startrow:end, startcol)), 1);
selecteddata = raw(startrow:endrow, :)
%or
selecteddata = cell2table(raw(startrow+1:endrow, :), 'VariableNames', matlab.lang.makeValidName(raw(startrow, :)))