请教高手，为啥我的vba 运行中 “未响应 ”一会？

请教高手，为啥我的vba 运行中 “未响应 ”一会，然后忽然就得出结果呢？
sheet1:

sheet2:

Sub 统计()
Dim a%, b%, c%
dim dyg as range
'清空
For Each dyg In Range(Cells(1, 1), Cells(10, 10))
dyg = 0
Next
'统计
For a = 2 To 20
For b = 2 To 4
For c = 2 To 4
Cells(Sheet1.Cells(a + 1, b) + 1, Sheet1.Cells(a, c) + 1) = Cells(Sheet1.Cells(a + 1, b) + 1, Sheet1.Cells(a, c) + 1) + 1
Next
Next
Next
End Sub