diff --git a/public/form.js b/public/form.js
index 5f42c9f..889fbb3 100644
--- a/public/form.js
+++ b/public/form.js
@@ -656,7 +656,17 @@ ocForm.showLine = function(selectedValues, line, keys, widgets, canHide, separat
       }
     }
   }
-  
+  // After variable substitution, replace the $[[ ]] section with the calculated result.
+  line = line.replace(/\$\[\[(.*?)\]\]/g, (_, expr) => {
+    try {
+          // Return calculation result
+          return eval(expr);
+        } catch (e) {
+          // Nothing to do
+          return `$[[${expr}]]`;
+        }
+    });
+
   if (line) {
     selectedValues.push(line);
   }