diff --git a/src/java/org/apache/poi/ss/formula/ptg/Area3DPxg.java b/src/java/org/apache/poi/ss/formula/ptg/Area3DPxg.java
index 84872f57e..b02f3e184 100644
--- a/src/java/org/apache/poi/ss/formula/ptg/Area3DPxg.java
+++ b/src/java/org/apache/poi/ss/formula/ptg/Area3DPxg.java
@@ -28,7 +28,7 @@ import org.apache.poi.util.LittleEndianOutput;
  * <p>This is XSSF only, as it stores the sheet / book references
  *  in String form. The HSSF equivalent using indexes is {@link Area3DPtg}</p>
  */
-public final class Area3DPxg extends AreaPtgBase {
+public final class Area3DPxg extends AreaPtgBase implements Pxg {
     private int externalWorkbookNumber = -1;
     private String sheetName;
 
@@ -71,6 +71,10 @@ public final class Area3DPxg extends AreaPtgBase {
     public String getSheetName() {
         return sheetName;
     }
+    
+    public void setSheetName(String sheetName) {
+        this.sheetName = sheetName;
+    }
 
     public String format2DRefAsString() {
         return formatReferenceAsString();
diff --git a/src/java/org/apache/poi/ss/formula/ptg/Deleted3DPxg.java b/src/java/org/apache/poi/ss/formula/ptg/Deleted3DPxg.java
index 772e10b2f..147b329b7 100644
--- a/src/java/org/apache/poi/ss/formula/ptg/Deleted3DPxg.java
+++ b/src/java/org/apache/poi/ss/formula/ptg/Deleted3DPxg.java
@@ -24,7 +24,7 @@ import org.apache.poi.util.LittleEndianOutput;
 /**
  * An XSSF only representation of a reference to a deleted area
  */
-public final class Deleted3DPxg extends OperandPtg {
+public final class Deleted3DPxg extends OperandPtg implements Pxg {
     private int externalWorkbookNumber = -1;
     private String sheetName;
 
@@ -58,6 +58,10 @@ public final class Deleted3DPxg extends OperandPtg {
     public String getSheetName() {
         return sheetName;
     }
+    
+    public void setSheetName(String sheetName) {
+        this.sheetName = sheetName;
+    }
 
     public String toFormulaString() {
         StringBuffer sb = new StringBuffer();
diff --git a/src/java/org/apache/poi/ss/formula/ptg/NameXPxg.java b/src/java/org/apache/poi/ss/formula/ptg/NameXPxg.java
index 0a49b175f..bac4fbee2 100644
--- a/src/java/org/apache/poi/ss/formula/ptg/NameXPxg.java
+++ b/src/java/org/apache/poi/ss/formula/ptg/NameXPxg.java
@@ -26,7 +26,7 @@ import org.apache.poi.util.LittleEndianOutput;
  * <p>This is XSSF only, as it stores the sheet / book references
  *  in String form. The HSSF equivalent using indexes is {@link NameXPtg}</p>
  */
-public final class NameXPxg extends OperandPtg {
+public final class NameXPxg extends OperandPtg implements Pxg {
     private int externalWorkbookNumber = -1;
     private String sheetName;
     private String nameName;
@@ -66,6 +66,10 @@ public final class NameXPxg extends OperandPtg {
     public String getNameName() {
         return nameName;
     }
+    
+    public void setSheetName(String sheetName) {
+        this.sheetName = sheetName;
+    }
 
     public String toFormulaString() {
         StringBuffer sb = new StringBuffer();
diff --git a/src/java/org/apache/poi/ss/formula/ptg/Pxg.java b/src/java/org/apache/poi/ss/formula/ptg/Pxg.java
new file mode 100644
index 000000000..fa1c4ff07
--- /dev/null
+++ b/src/java/org/apache/poi/ss/formula/ptg/Pxg.java
@@ -0,0 +1,29 @@
+/* ====================================================================
+   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.ss.formula.ptg;
+
+/**
+ * An XSSF only special kind of Ptg, which stores the sheet / book 
+ *  reference in string form.
+ */
+public interface Pxg {
+    public int getExternalWorkbookNumber();
+    public String getSheetName();
+    public void setSheetName(String sheetName);
+    public String toFormulaString();
+}
diff --git a/src/java/org/apache/poi/ss/formula/ptg/Ref3DPxg.java b/src/java/org/apache/poi/ss/formula/ptg/Ref3DPxg.java
index ed95892fb..9a2dc606f 100644
--- a/src/java/org/apache/poi/ss/formula/ptg/Ref3DPxg.java
+++ b/src/java/org/apache/poi/ss/formula/ptg/Ref3DPxg.java
@@ -28,7 +28,7 @@ import org.apache.poi.util.LittleEndianOutput;
  * <p>This is XSSF only, as it stores the sheet / book references
  *  in String form. The HSSF equivalent using indexes is {@link Ref3DPtg}</p>
  */
-public final class Ref3DPxg extends RefPtgBase {
+public final class Ref3DPxg extends RefPtgBase implements Pxg {
     private int externalWorkbookNumber = -1;
     private String sheetName;
 
@@ -71,6 +71,10 @@ public final class Ref3DPxg extends RefPtgBase {
         return sheetName;
     }
     
+    public void setSheetName(String sheetName) {
+        this.sheetName = sheetName;
+    }
+    
     public String format2DRefAsString() {
         return formatReferenceAsString();
     }