you can easily achieve this with a function node...
Demo flow
[{"id":"fb21b077.e82d8","type":"inject","z":"59c1e9ca.dd6988","name":"every 15m","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"0.5","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":630,"y":940,"wires":[["9c7b3790.838ae8"]]},{"id":"f8cb95c9.09e8f8","type":"debug","z":"59c1e9ca.dd6988","name":"to message sender","active":true,"tosidebar":false,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":1050,"y":940,"wires":[]},{"id":"9c7b3790.838ae8","type":"function","z":"59c1e9ca.dd6988","name":"block/unblock","func":"var block = context.get(\"block\") || false;\n\nif (msg.topic == \"block\") {\n block = true;\n node.status({fill:\"red\",shape:\"ring\",text:\"blocked\"});\n} else if (msg.topic == \"unblock\") {\n block = false;\n node.status({});//clear status\n}\n\ncontext.set(\"block\", block);\n\nif(block) return null; //halt the flow\n\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":830,"y":940,"wires":[["f8cb95c9.09e8f8"]]},{"id":"55a14164.9d978","type":"inject","z":"59c1e9ca.dd6988","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"block","payload":"","payloadType":"str","x":610,"y":1000,"wires":[["9c7b3790.838ae8"]]},{"id":"a1cef437.a22018","type":"inject","z":"59c1e9ca.dd6988","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"unblock","payload":"","payloadType":"str","x":620,"y":1040,"wires":[["9c7b3790.838ae8"]]}]
