diff --git a/src/data.cpp b/src/data.cpp
index 8a389a4..e1de3e4 100644
--- a/src/data.cpp
+++ b/src/data.cpp
@@ -209,6 +209,14 @@ bool Value::isMarked(bool parents, bool children) const
     return false;
 }
 
+Value Value::ifMarked(bool parents, bool children) const
+{
+    Value ret;
+    if(isMarked(parents, children))
+        ret = *this;
+    return ret;
+}
+
 void Value::mark(bool v)
 {
     if(!desc)
diff --git a/src/pvxs/data.h b/src/pvxs/data.h
index b94dcee..0122257 100644
--- a/src/pvxs/data.h
+++ b/src/pvxs/data.h
@@ -508,6 +508,8 @@ public:
 
     //! Test if this field is marked as valid/changed
     bool isMarked(bool parents=true, bool children=false) const;
+    //! return *this if isMarked()==true, or a !valid() ref. if false.
+    Value ifMarked(bool parents=true, bool children=false) const;
     //! Mark this field as valid/changed
     void mark(bool v=true);
     //! Remove mark from this field