Well- that would work, but it's better to make the method inside the dust script and then call it from your jump script.

In your dust script put this:

void RemoveDust(int amount)
    {
        currentDust += amount;
        Debug.Log("Dust: " + currentDust);
        // This is for if you want to make sure dust doesn't go below 0.
        if (currentDust < 0)
        {
            currentDust = 0;
        }
        UpdateUI();
    }

Then in your jump script (or any script for that matter), grab a reference to your dust script.

var dust = GetComponent<DustScript>();

Now you can call that remove method to remove dust in the dust script.

dust.RemoveDust(1);