title: POI cell.setCellFormula cause "Name 'MY_FUNC' is completely unknown in the current workbook" error
body: <p>I want to use POI setCellFormula to set a formula to an cell, the formula is from a excel add-in but not currently installed. After that, I'll move the excel to a PC with the add-in installed to evaluate the formulas.</p>
  
  <p>However, when I try to set the formula using setCellFormula, I get an exception:</p>
  
  <p>Exception in thread "main" org.apache.poi.ss.formula.FormulaParseException: Name 'MY_FUNC' is completely unknown in the current workbook
      at org.apache.poi.ss.formula.FormulaParser.function(FormulaParser.java:918)
      at org.apache.poi.ss.formula.FormulaParser.parseNonRange(FormulaParser.java:556)
      at org.apache.poi.ss.formula.FormulaParser.parseRangeable(FormulaParser.java:427)
      at org.apache.poi.ss.formula.FormulaParser.parseRangeExpression(FormulaParser.java:266)
      at org.apache.poi.ss.formula.FormulaParser.parseSimpleFactor(FormulaParser.java:1117)
      at org.apache.poi.ss.formula.FormulaParser.percentFactor(FormulaParser.java:1077)
      at org.apache.poi.ss.formula.FormulaParser.powerFactor(FormulaParser.java:1064)
      at org.apache.poi.ss.formula.FormulaParser.Term(FormulaParser.java:1424)
      at org.apache.poi.ss.formula.FormulaParser.additiveExpression(FormulaParser.java:1524)
      at org.apache.poi.ss.formula.FormulaParser.concatExpression(FormulaParser.java:1508)
      at org.apache.poi.ss.formula.FormulaParser.comparisonExpression(FormulaParser.java:1465)
      at org.apache.poi.ss.formula.FormulaParser.unionExpression(FormulaParser.java:1445)
      at org.apache.poi.ss.formula.FormulaParser.parse(FormulaParser.java:1566)
      at org.apache.poi.ss.formula.FormulaParser.parse(FormulaParser.java:174)
      at org.apache.poi.hssf.model.HSSFFormulaParser.parse(HSSFFormulaParser.java:72)
      at org.apache.poi.hssf.usermodel.HSSFCell.setCellFormula(HSSFCell.java:605)</p>
  
  <p>Is there a way that I set the formula without evaluate it immediately?</p>