diff --git a/samples/ConditionalFormatting/07_Expression_Comparisons.php b/samples/ConditionalFormatting/07_Expression_Comparisons.php
index 88d79b23..43d6fe56 100644
--- a/samples/ConditionalFormatting/07_Expression_Comparisons.php
+++ b/samples/ConditionalFormatting/07_Expression_Comparisons.php
@@ -28,6 +28,7 @@ $helper->log('Add data');
 $spreadsheet->setActiveSheetIndex(0);
 $spreadsheet->getActiveSheet()
     ->setCellValue('A1', 'Odd/Even Expression Comparison')
+    ->setCellValue('A4', 'Note that these functions are not available for Xls files')
     ->setCellValue('A15', 'Sales Grid Expression Comparison')
     ->setCellValue('A25', 'Sales Grid Multiple Expression Comparison');
 
@@ -101,9 +102,9 @@ $expressionWizard->expression('ISEVEN(A1)')
     ->setStyle($yellowStyle);
 $conditionalStyles[] = $expressionWizard->getConditional();
 
-$spreadsheet->getActiveSheet()
-    ->getStyle($expressionWizard->getCellRange())
-    ->setConditionalStyles($conditionalStyles);
+//$spreadsheet->getActiveSheet()
+//    ->getStyle($expressionWizard->getCellRange())
+//    ->setConditionalStyles($conditionalStyles);
 
 // Set rules for Sales Grid Row match against Country Comparison
 $cellRange = 'A17:D22';
diff --git a/src/PhpSpreadsheet/Style/ConditionalFormatting/Wizard/WizardAbstract.php b/src/PhpSpreadsheet/Style/ConditionalFormatting/Wizard/WizardAbstract.php
index 75d6856e..df9daab3 100644
--- a/src/PhpSpreadsheet/Style/ConditionalFormatting/Wizard/WizardAbstract.php
+++ b/src/PhpSpreadsheet/Style/ConditionalFormatting/Wizard/WizardAbstract.php
@@ -122,7 +122,7 @@ abstract class WizardAbstract
         return "{$worksheet}{$column}{$row}";
     }
 
-    protected static function reverseAdjustCellRef(string $condition, string $cellRange): string
+    public static function reverseAdjustCellRef(string $condition, string $cellRange): string
     {
         $conditionalRange = Coordinate::splitRange(str_replace('$', '', strtoupper($cellRange)));
         [$referenceCell] = $conditionalRange[0];
diff --git a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
index c02e3420..ecfc1a6a 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Worksheet.php
@@ -13,6 +13,7 @@ use PhpOffice\PhpSpreadsheet\Shared\Xls;
 use PhpOffice\PhpSpreadsheet\Style\Border;
 use PhpOffice\PhpSpreadsheet\Style\Color;
 use PhpOffice\PhpSpreadsheet\Style\Conditional;
+use PhpOffice\PhpSpreadsheet\Style\ConditionalFormatting\Wizard;
 use PhpOffice\PhpSpreadsheet\Style\Protection;
 use PhpOffice\PhpSpreadsheet\Worksheet\PageSetup;
 use PhpOffice\PhpSpreadsheet\Worksheet\SheetView;
@@ -569,7 +570,7 @@ class Worksheet extends BIFFwriter
                             $arrConditional[$conditional->getHashCode()] = true;
 
                             // Write CFRULE record
-                            $this->writeCFRule($conditional);
+                            $this->writeCFRule($conditional, $cellCoordinate);
                         }
                     }
                 }
@@ -2779,7 +2780,7 @@ class Worksheet extends BIFFwriter
     /**
      * Write CFRule Record.
      */
-    private function writeCFRule(Conditional $conditional): void
+    private function writeCFRule(Conditional $conditional, string $cellRange): void
     {
         $record = 0x01B1; // Record identifier
         $type = null;  //  Type of the CF
@@ -2832,21 +2833,59 @@ class Worksheet extends BIFFwriter
         // $szValue2 : size of the formula data for second value or formula
         $arrConditions = $conditional->getConditions();
         $numConditions = count($arrConditions);
+
+        $szValue1 = 0x0000;
+        $szValue2 = 0x0000;
+        $operand1 = null;
+        $operand2 = null;
+
         if ($numConditions == 1) {
-            $szValue1 = ($arrConditions[0] <= 65535 ? 3 : 0x0000);
-            $szValue2 = 0x0000;
-            $operand1 = pack('Cv', 0x1E, $arrConditions[0]);
-            $operand2 = null;
+            if (is_int($arrConditions[0]) || is_float($arrConditions[0])) {
+                $szValue1 = ($arrConditions[0] <= 65535 ? 3 : 0x0000);
+                $operand1 = pack('Cv', 0x1E, $arrConditions[0]);
+            } else {
+                try {
+                    $formula1 = Wizard\WizardAbstract::reverseAdjustCellRef((string) $arrConditions[0], $cellRange);
+                    $this->parser->parse($formula1);
+                    $formula1 = $this->parser->toReversePolish();
+                    $szValue1 = strlen($formula1);
+                } catch (PhpSpreadsheetException $e) {
+                    var_dump("PARSER EXCEPTION: {$e->getMessage()}");
+                    $formula1 = null;
+                }
+                $operand1 = $formula1;
+            }
         } elseif ($numConditions == 2 && ($conditional->getOperatorType() == Conditional::OPERATOR_BETWEEN)) {
-            $szValue1 = ($arrConditions[0] <= 65535 ? 3 : 0x0000);
-            $szValue2 = ($arrConditions[1] <= 65535 ? 3 : 0x0000);
-            $operand1 = pack('Cv', 0x1E, $arrConditions[0]);
-            $operand2 = pack('Cv', 0x1E, $arrConditions[1]);
-        } else {
-            $szValue1 = 0x0000;
-            $szValue2 = 0x0000;
-            $operand1 = null;
-            $operand2 = null;
+            if (is_int($arrConditions[0]) || is_float($arrConditions[0])) {
+                $szValue1 = ($arrConditions[0] <= 65535 ? 3 : 0x0000);
+                $operand1 = pack('Cv', 0x1E, $arrConditions[0]);
+            } else {
+                try {
+                    $formula1 = Wizard\WizardAbstract::reverseAdjustCellRef((string) $arrConditions[0], $cellRange);
+                    $this->parser->parse($formula1);
+                    $formula1 = $this->parser->toReversePolish();
+                    $szValue1 = strlen($formula1);
+                } catch (PhpSpreadsheetException $e) {
+                    var_dump("PARSER EXCEPTION: {$e->getMessage()}");
+                    $formula1 = null;
+                }
+                $operand1 = $formula1;
+            }
+            if (is_int($arrConditions[1]) || is_float($arrConditions[1])) {
+                $szValue2 = ($arrConditions[1] <= 65535 ? 3 : 0x0000);
+                $operand2 = pack('Cv', 0x1E, $arrConditions[1]);
+            } else {
+                try {
+                    $formula2 = Wizard\WizardAbstract::reverseAdjustCellRef((string) $arrConditions[1], $cellRange);
+                    $this->parser->parse($formula2);
+                    $formula2 = $this->parser->toReversePolish();
+                    $szValue2 = strlen($formula2);
+                } catch (PhpSpreadsheetException $e) {
+                    var_dump("PARSER EXCEPTION: {$e->getMessage()}");
+                    $formula2 = null;
+                }
+                $operand2 = $formula2;
+            }
         }
 
         // $flags : Option flags