private void updateRowFormulas(XSSFRow row, FormulaShifter shifter) {
for (Cell c : row) {
XSSFCell cell = (XSSFCell) c;
CTCell ctCell = cell.getCTCell();
if (ctCell.isSetF()) {
CTCellFormula f = ctCell.getF();
String formula = f.getStringValue();
if (formula.length() > 0) {
String shiftedFormula = shiftFormula(row, formula, shifter);
if (shiftedFormula != null) {
f.setStringValue(shiftedFormula);