<button @click="btn">클릭</button>  
(...)
btn(){          
// workerGrid는 grid의 인스턴스
this.workerGrid.collectionView.sourceCollection[0].checks[0].earnings.push({hours:30,name:"extra",rate:30}); // 데이터 삽입
        this.workerGrid.collectionView.refresh() // 새로고침
    },