* Returns true indicate spreadsheet index column/row is number
* @return
*/
private boolean isAllCellNumberType(int idx) {
Worksheet sheet = ss.getSelectedSheet();
Rect rect = ss.getSelection();
int top = sortOrientation ? idx : rect.getTop();
int left = sortOrientation ? rect.getLeft() : idx;
int bottom = sortOrientation ? idx : rect.getBottom();
int right = sortOrientation ? rect.getRight() : idx;
for (int row = top; row <= bottom; row++) {
for (int col = left; col <= right; col++) {
Cell c = Utils.getCell(sheet, row, col);
if (c != null) {