Eloquent relation with custom foreign - other key value

Is there a way to create an Eloquent relation function based on custom foreign - other key value?

For example I have level relation:

public function level(){
    return $this->belongsTo(Level::class, 'level_number', 'number');
}

And I want to do something like this:

public function nextLevel(){
    return $this->belongsTo(Level::class)->where('number', '=', $this->level_number + 1);
}

Is this possible or I have to write a raw query?

via Chebli Mohamed