diff --git a/api/js/etemplate/et2_widget_textbox.js b/api/js/etemplate/et2_widget_textbox.js
index 084b6eabbc..3fe4e71d48 100644
--- a/api/js/etemplate/et2_widget_textbox.js
+++ b/api/js/etemplate/et2_widget_textbox.js
@@ -249,6 +249,7 @@ var et2_textbox = (function(){ "use strict"; return et2_inputWidget.extend([et2_
 	 */
 	set_readonly: function(_readonly) {
 		this.input.attr("readonly", _readonly);
+		this.input.toggleClass('et2_textbox_ro', _readonly);
 	},
 
 	set_blur: function(_value) {
diff --git a/calendar/js/app.js b/calendar/js/app.js
index cc5b89aedf..6da8c3a0e7 100644
--- a/calendar/js/app.js
+++ b/calendar/js/app.js
@@ -1121,15 +1121,36 @@ app.classes.calendar = (function(){ "use strict"; return AppJS.extend(
 	},
 
 	/**
-	 * Change participant add button status based on
-	 * participants field value
+	 * On change participant event, try to set add button status based on
+	 * participant field value. Additionally, disable/enable quantity field
+	 * if there's none resource value or there are more than one resource selected.
 	 *
 	 */
-	participantOnChange: function () {
+	participantOnChange: function ()
+	{
 		var add = this.et2.getWidgetById('add');
+		var quantity = this.et2.getWidgetById('quantity');
 		var participant = this.et2.getWidgetById('participant');
 
-		add.set_readonly(participant.get_value().length <= 0);
+		// array of participants
+		var value = participant.get_value();
+
+		add.set_readonly(value.length <= 0);
+
+		quantity.set_readonly(false);
+
+		// number of resources
+		var nRes = 0;
+
+		for (var i=0;i<value.length;i++)
+		{
+			if (!value[i].match(/\D/ig) || nRes)
+			{
+				quantity.set_readonly(true);
+				quantity.set_value(1);
+			}
+			nRes++;
+		}
 	},
 
 	/**
diff --git a/calendar/templates/default/app.css b/calendar/templates/default/app.css
index 69661f7be0..e70fabd4ad 100644
--- a/calendar/templates/default/app.css
+++ b/calendar/templates/default/app.css
@@ -1435,4 +1435,6 @@ input#calendar-edit_location {padding-left: 0;}
 	{
 		display:inline;
 	}
-}
\ No newline at end of file
+}
+
+#calendar-edit_quantity.et2_textbox_ro {opacity:0.5;}
\ No newline at end of file
diff --git a/calendar/templates/pixelegg/app.css b/calendar/templates/pixelegg/app.css
index d8f0fef7ac..2c84367fc1 100755
--- a/calendar/templates/pixelegg/app.css
+++ b/calendar/templates/pixelegg/app.css
@@ -11,7 +11,7 @@
  * @package calendar
  * @version $Id$
  */
-/* $Id: app.css 55840 2016-04-25 22:09:57Z nathangray $ */
+/* $Id: app.css 55869 2016-04-26 22:58:35Z nathangray $ */
 /*Media print classes*/
 @media print {
   #calendar-view.et2_container,
@@ -1394,6 +1394,9 @@ input#calendar-edit_location {
     display: inline;
   }
 }
+#calendar-edit_quantity.et2_textbox_ro {
+  opacity: 0.5;
+}
 /*generell*/
 .egw_fw_content_browser_iframe img[src$="svg"] {
   background-color: #828282 !important;
@@ -2624,5 +2627,3 @@ div#calendar-container div.calendar table tbody tr.rowhilite td {
 #calendar_merge {
   margin: 9px 0 0 0;
 }
-/* ########################################################################################
-/* * Calendar END */