Set variable in Change Node JSON

may bee a simple question - i have a change node:
image
with the following JSON:

{
    "args": [
        21
    ]
}

now i have to set the "21" dynamicly e.g. with msg.payload. If i do so i get an error "Invalid Token".
Or can i do thse same with a function node?

Thanks for any help
BR
Hubertus

Change the type of the field to "Expression" and replace the 21 with payload.

Thank you . sometimes it's simple :wink:
Have a nice weekend