diff --git a/README.md b/README.md
index fb06d67..3236120 100644
--- a/README.md
+++ b/README.md
@@ -180,7 +180,7 @@ then
 
 * the dropdown menu button is placed in the panel at `POSITION`, and
 * the plugin is re-run and its output re-rendered every `INTERVAL`, and
-* if `INTERVAL` is followed by `+`, the plugin is additionally re-run each time the dropdown menu is opened.
+* if `INTERVAL` is followed by `+`, the plugin is additionally re-run each time the dropdown menu is opened. if `INTERVAL` is followed by `-`, the plugin is only run when the dropdown menu is opened.
 
 `POSITION` may be omitted entirely (in which case the button is placed before all other buttons on the right-hand side of the panel) while `INTERVAL` can be left empty. For example, a script named `plugin.10s.sh` is updated every 10 seconds, the button belonging to `plugin.1c..sh` is positioned just right of the GNOME Shell clock, and `plugin.l.1m.sh` is displayed left of the "Activities" button and updated every minute.
 
diff --git a/argos@pew.worldwidemann.com/button.js b/argos@pew.worldwidemann.com/button.js
index cd7bec2..72f5b19 100644
--- a/argos@pew.worldwidemann.com/button.js
+++ b/argos@pew.worldwidemann.com/button.js
@@ -30,6 +30,7 @@ var ArgosButton = new Lang.Class({
 
     this._file = file;
     this._updateInterval = settings.updateInterval;
+    this._updateOnClose = settings.updateOnClose;
 
     this._lineView = new ArgosLineView();
     this._lineView.setMarkup("<small><i>" + GLib.markup_escape_text(file.get_basename(), -1) + " ...</i></small>");
@@ -94,7 +95,7 @@ var ArgosButton = new Lang.Class({
 
           this._processOutput(standardOutput.split("\n"));
 
-          if (this._updateInterval !== null) {
+          if (this._updateInterval !== null && (this.menu.isOpen || (!this.menu.isOpen && this._updateOnClose))) {
             this._updateTimeout = Mainloop.timeout_add_seconds(this._updateInterval, Lang.bind(this, function() {
               this._updateTimeout = null;
               this._update();
diff --git a/argos@pew.worldwidemann.com/utilities.js b/argos@pew.worldwidemann.com/utilities.js
index 5cb795f..ba8310e 100644
--- a/argos@pew.worldwidemann.com/utilities.js
+++ b/argos@pew.worldwidemann.com/utilities.js
@@ -24,6 +24,7 @@ const BOXES = {
 function parseFilename(filename) {
   let settings = {
     updateOnOpen: false,
+    updateOnClose: true,
     updateInterval: null,
     position: 0,
     box: "right"
@@ -39,6 +40,12 @@ function parseFilename(filename) {
     updatePart = updatePart.substring(0, updatePart.length - 1);
   }
 
+  if (updatePart !== null && updatePart.endsWith("-")) {
+    settings.updateOnClose = false;
+    settings.updateOnOpen = true;
+    updatePart = updatePart.substring(0, updatePart.length - 1);
+  }
+
   if (updatePart !== null && updatePart.length >= 2) {
     // Attempt to parse BitBar refresh time string
     let number = updatePart.substring(0, updatePart.length - 1);