--- src/java/org/apache/poi/hssf/record/formula/eval/FunctionEval.java	(revision 829277)
+++ src/java/org/apache/poi/hssf/record/formula/eval/FunctionEval.java	(working copy)
@@ -203,6 +203,7 @@ 
 
 		retval[345] = new Sumif();
 		retval[346] = new Countif();
+		retval[347] = new Countblank();
 
 		retval[359] = new Hyperlink();
 
--- src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java	(revision 0)
+++ src/java/org/apache/poi/hssf/record/formula/functions/Countblank.java	(revision 0)
@@ -0,0 +1,73 @@ 
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+package org.apache.poi.hssf.record.formula.functions;
+
+import org.apache.poi.hssf.record.formula.eval.AreaEval;
+import org.apache.poi.hssf.record.formula.eval.BlankEval;
+import org.apache.poi.hssf.record.formula.eval.ErrorEval;
+import org.apache.poi.hssf.record.formula.eval.NumberEval;
+import org.apache.poi.hssf.record.formula.eval.RefEval;
+import org.apache.poi.hssf.record.formula.eval.ValueEval;
+import org.apache.poi.hssf.record.formula.functions.CountUtils.I_MatchPredicate;
+
+/**
+ * Implementation for the function COUNTBLANK
+ * <p>
+ *  Syntax: COUNTBLANK ( range )
+ *    <table border="0" cellpadding="1" cellspacing="0" summary="Parameter descriptions">
+ *      <tr><th>range&nbsp;&nbsp;&nbsp;</th><td>is the range of cells to count blanks</td></tr>
+ *    </table>
+ * </p>
+ *
+ * @author Mads Mohr Christensen
+ */
+public final class Countblank implements Function {
+
+	public ValueEval evaluate(ValueEval[] args, int srcRowIndex, short srcColumnIndex) {
+		switch(args.length) {
+		case 1:
+			// expected
+			break;
+		default:
+			// TODO - it doesn't seem to be possible to enter COUNTBLANK() into Excel with the wrong arg count
+			// perhaps this should be an exception
+			return ErrorEval.VALUE_INVALID;
+		}
+
+		double result;
+		if (args[0] instanceof RefEval) {
+			result = CountUtils.countMatchingCell((RefEval) args[0], predicate);
+		} else if (args[0] instanceof AreaEval) {
+			result = CountUtils.countMatchingCellsInArea((AreaEval) args[0], predicate);
+		} else {
+			throw new IllegalArgumentException("Bad range arg type (" + args[0].getClass().getName() + ")");
+		}
+		return new NumberEval(result);
+	}
+
+	private static final I_MatchPredicate predicate = new I_MatchPredicate() {
+
+		public boolean matches(ValueEval valueEval) {
+			if(valueEval == BlankEval.INSTANCE) {
+				return true;
+			}
+			// Note - only BlankEval counts
+			return false;
+		}
+	};
+}
--- src/testcases/org/apache/poi/hssf/record/formula/functions/TestCountFuncs.java	(revision 829277)
+++ src/testcases/org/apache/poi/hssf/record/formula/functions/TestCountFuncs.java	(working copy)
@@ -45,7 +45,35 @@ 
 public final class TestCountFuncs extends TestCase {
 
 	private static final String NULL = null;
+	
+	public void testCountBlank() {
 
+		AreaEval range;
+		ValueEval[] values;
+
+		values = new ValueEval[] {
+				new NumberEval(0),
+				new StringEval(""),	// note - does not match blank
+				BoolEval.TRUE,
+				BoolEval.FALSE,
+				ErrorEval.DIV_ZERO,
+				BlankEval.INSTANCE,
+		};
+		range = EvalFactory.createAreaEval("A1:B3", values);
+		confirmCountBlank(1, range);
+		
+		values = new ValueEval[] {
+				new NumberEval(0),
+				new StringEval(""),	// note - does not match blank
+				BlankEval.INSTANCE,
+				BoolEval.FALSE,
+				BoolEval.TRUE,
+				BlankEval.INSTANCE,
+		};
+		range = EvalFactory.createAreaEval("A1:B3", values);
+		confirmCountBlank(2, range);
+	}
+
 	public void testCountA() {
 
 		ValueEval[] args;
@@ -196,6 +224,12 @@ 
 		double result = NumericFunctionInvoker.invoke(new Countif(), args);
 		assertEquals(expected, result, 0);
 	}
+	private static void confirmCountBlank(int expected, AreaEval range) {
+		
+		ValueEval[] args = { range };
+		double result = NumericFunctionInvoker.invoke(new Countblank(), args);
+		assertEquals(expected, result, 0);
+	}
 
 	private static I_MatchPredicate createCriteriaPredicate(ValueEval ev) {
 		return Countif.createCriteriaPredicate(ev, 0, 0);
@@ -418,4 +452,36 @@ 
 			throw new AssertionFailedError(failureCount + " countif evaluations failed. See stderr for more details");
 		}
 	}
+	
+	public void testCounBlankFromSpreadsheet() {
+		final String FILE_NAME = "countblankExamples.xls";
+		final int START_ROW_IX = 1;
+		final int COL_IX_ACTUAL = 3;
+		final int COL_IX_EXPECTED = 4;
+
+		int failureCount = 0;
+		HSSFWorkbook wb = HSSFTestDataSamples.openSampleWorkbook(FILE_NAME);
+		HSSFSheet sheet = wb.getSheetAt(0);
+		HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+		int maxRow = sheet.getLastRowNum();
+		for (int rowIx=START_ROW_IX; rowIx<maxRow; rowIx++) {
+			HSSFRow row = sheet.getRow(rowIx);
+			if(row == null) {
+				continue;
+			}
+			HSSFCell cell = row.getCell(COL_IX_ACTUAL);
+			CellValue cv = fe.evaluate(cell);
+			double actualValue = cv.getNumberValue();
+			double expectedValue = row.getCell(COL_IX_EXPECTED).getNumericCellValue();
+			if (actualValue != expectedValue) {
+				System.err.println("Problem with test case on row " + (rowIx+1) + " "
+						+ "Expected = (" + expectedValue + ") Actual=(" + actualValue + ") ");
+				failureCount++;
+			}
+		}
+
+		if (failureCount > 0) {
+			throw new AssertionFailedError(failureCount + " countblank evaluations failed. See stderr for more details");
+		}
+	}
 }