Trigger to update only on nesten property

MongoDB Atlas
1

Hi.
I want to create a trigger on document update, but only when a nesten property is changed.
Example: Only when this property change:

"modelProperties": { 
    "property": { 
        "serialnumber": "1234" 
        }
    }

And i dont want the trigger to activate when any other properties under “modelProperties” or “property” changes.

How do I set up $match and $project? I have tried several options without luck, looks like as long as anything changes in the object “modelProperties” the trigger activates.

Here what this document might look like:

{
    "_id":{
    "$oid":"613f0e85621128bc1d4f7241"
    },
    "name":"=310.001-SG001",
    "description":"Main backflow preventer",
    "modelId":"6107ae6a47dab80394029163",
    "modelName":"Backflow preventer",
    "tenantId":"60d5cb6f490e691fe00b7558",
    "modelProperties":{
        "property":{
            "tagnumber":"=310.001-SG001",
            "location":"Room 001",
            "modelNumber":"Resideo/cccxxxx",
            "serialNumber":"123456",
            "installationDate":"2021-08-10",
            "inspectionInterval":6,
            "maintenanceInterval":"12",
            "expectedLife":"10",
            "expectedEndOfLife":"2031-08-10",
            "pressureCapacity":10,
            "pipeDiameter":45,
            "flowCapacity":16,
            "tagNumber":"=310.001-SG001",
            "manufacturer":"Honeywell",
            "lastInspection":"2021-09-27",
            "lastMaintenance":"2021-05-04",
            "nextInspection":"2022-03-27",
            "nextMaintenance":"2022-05-04"
        },
        "command":{
            "Close":"true",
            "Close description":"test"
        },
        "telemetry":{},
        "component":{},
        "relationship":{}
    }
}

Any help is appreciated, thank you in advance.