Update ua_client_highlevel.h

include/ua_client_highlevel.h

@@ -280,7 +280,7 @@ void UA_EXPORT UA_Client_Subscriptions_manuallySendPublishRequest(UA_Client *cli
 UA_StatusCode UA_EXPORT
 UA_Client_Subscriptions_addMonitoredItem(UA_Client *client, UA_UInt32 subscriptionId,
                                          UA_NodeId nodeId, UA_UInt32 attributeID,
-                                         void *handlingFunction, void *handlingContext,
+                                         void (*handlingFunction)(UA_UInt32 handle, UA_DataValue *value, void *context), void *handlingContext,
                                          UA_UInt32 *newMonitoredItemId);
 
 UA_StatusCode UA_EXPORT