I am writing a Javascript function that will be a tag in Google Tag Manager.

It is loaded on a SPA which I have minimal control over.

Whenever a user clicks, I use the GTM functionality to push some data to the datalayer, e.g.:

```
var someEventIsTriggered = function(e) {
        var target = $('input#watched');

        // Trigger a generic "gtm.click" event on every click
        dataLayer.push({
            "event": "gtm.customEvent",
            "gtm.customWatchedVariable": target.val()
        });
};

```

Every time this is triggered, it will push a new event to the datalayer, and updated the value of gtm.customWatchedVariable. What I now want to check is if the current `gtm.customWatchedVariable` is different from the last `gtm.customWatchedVariable`, and then fire a Trigger in GTM when it changes.

How can I do this?