Index: lams_tool_assessment/conf/language/lams/ApplicationResources.properties
===================================================================
diff -u -r2485ce33e55a921bdcde94e4f242da5da3cf1fc4 -r6fa531a730e4c685bcec3569ae46c98ea9f51571
--- lams_tool_assessment/conf/language/lams/ApplicationResources.properties	(.../ApplicationResources.properties)	(revision 2485ce33e55a921bdcde94e4f242da5da3cf1fc4)
+++ lams_tool_assessment/conf/language/lams/ApplicationResources.properties	(.../ApplicationResources.properties)	(revision 6fa531a730e4c685bcec3569ae46c98ea9f51571)
@@ -291,6 +291,7 @@
 output.desc.best.score  =Best score
 output.desc.none =No score
 label.tool.output.has.been.changed  =Tool Output has been changed
+warn.tool.output.change.none =This will delete all existing marks for this activity. Are you sure?
 output.desc.first.score  =First score
 output.desc.average.score  =Average score
 label.waiting.for.leader.launch.time.limit  =Leader has not started the activity. Please wait until he/she commences it.
Index: lams_tool_assessment/web/pages/monitoring/statisticpart.jsp
===================================================================
diff -u -r2485ce33e55a921bdcde94e4f242da5da3cf1fc4 -r6fa531a730e4c685bcec3569ae46c98ea9f51571
--- lams_tool_assessment/web/pages/monitoring/statisticpart.jsp	(.../statisticpart.jsp)	(revision 2485ce33e55a921bdcde94e4f242da5da3cf1fc4)
+++ lams_tool_assessment/web/pages/monitoring/statisticpart.jsp	(.../statisticpart.jsp)	(revision 6fa531a730e4c685bcec3569ae46c98ea9f51571)
@@ -6,7 +6,14 @@
 <script type="text/javascript">
 	$(document).ready(function(){
 		
-		$('#activity-evaluation').on('change', function() {
+		$('#activity-evaluation').on('focus', function(){
+			$(this).data('previousValue', this.value);
+		}).on('change', function() {
+			if (!this.value && !confirm("<fmt:message key='warn.tool.output.change.none'/>")) {
+				$(this).val($(this).data('previousValue'));
+				return;
+			}
+			$(this).data('previousValue', this.value);
 			$.ajax({
 				url: '<c:url value="/monitoring/setActivityEvaluation.do?sessionMapID=${sessionMapID}"/>',
 				data: {
Index: lams_tool_lamc/conf/language/lams/ApplicationResources.properties
===================================================================
diff -u -r2485ce33e55a921bdcde94e4f242da5da3cf1fc4 -r6fa531a730e4c685bcec3569ae46c98ea9f51571
--- lams_tool_lamc/conf/language/lams/ApplicationResources.properties	(.../ApplicationResources.properties)	(revision 2485ce33e55a921bdcde94e4f242da5da3cf1fc4)
+++ lams_tool_lamc/conf/language/lams/ApplicationResources.properties	(.../ApplicationResources.properties)	(revision 6fa531a730e4c685bcec3569ae46c98ea9f51571)
@@ -199,6 +199,7 @@
 label.question.options  =Question options
 label.activity.completion  =End of activity
 label.tool.output  =Tool output
+warn.tool.output.change.none =This will delete all existing marks for this activity. Are you sure?
 label.tool.output.has.been.changed  =Tool output has changed
 label.operation.failed  =Operation failed
 answers.submitted.none  =Select at least one answer for each of the questions.
Index: lams_tool_lamc/web/monitoring/parts/statsPart.jsp
===================================================================
diff -u -r2485ce33e55a921bdcde94e4f242da5da3cf1fc4 -r6fa531a730e4c685bcec3569ae46c98ea9f51571
--- lams_tool_lamc/web/monitoring/parts/statsPart.jsp	(.../statsPart.jsp)	(revision 2485ce33e55a921bdcde94e4f242da5da3cf1fc4)
+++ lams_tool_lamc/web/monitoring/parts/statsPart.jsp	(.../statsPart.jsp)	(revision 6fa531a730e4c685bcec3569ae46c98ea9f51571)
@@ -5,7 +5,14 @@
 <script type="text/javascript">
 	$(document).ready(function(){
 		
-		$('#activity-evaluation').on('change', function() {
+		$('#activity-evaluation').on('focus', function(){
+			$(this).data('previousValue', this.value);
+		}).on('change', function() {
+			if (!this.value && !confirm("<fmt:message key='warn.tool.output.change.none'/>")) {
+				$(this).val($(this).data('previousValue'));
+				return;
+			}
+			$(this).data('previousValue', this.value);
 			$.ajax({
 				url: '<c:url value="/monitoring.do"/>',
 				data: {