为什么这两个代码运行速度差那么远呢？

YMOON1986

第一个只要2秒多，第二个要22秒多
Sub h()
t = Timer
Dim i As Range, b As Range, bb As Range
Application.Calculation = xlManual
Application.ScreenUpdating = False

For Each i In Selection
    For Each b In Range("a" & i.Row & ":p" & i.Row)
        If b <> "" Then
            a = a & "+" & b
        End If
    Next b
    Cells(i.Row, 17) = "=" & a
    a = ""
Next i
For Each bb In Selection
    If bb = "=" Then
        bb = ""
    End If
Next bb
[a1].Copy [q1]
[q:q].Select
Application.Calculation = xlAutomatic
Application.ScreenUpdating = True
MsgBox Format(Timer - t, "0.0000")
End Sub


Sub v()
t = Timer
Dim i As Range, b As Range, bb As Range
Application.Calculation = xlManual
Application.ScreenUpdating = False
Set lastcell = Cells(Rows.Count, "a").End(xlUp)
For Each i In Range([q2], lastcell)
    For Each b In Range("a" & i.Row & ":p" & i.Row)
        If b <> "" Then
            a = a & "+" & b
        End If
    Next b
    Cells(i.Row, 17) = "=" & a
    a = ""
Next i
For Each bb In Range([q2], lastcell)
    If bb = "=" Then
        bb = ""
    End If
Next bb
[a1].Copy [q1]
[q:q].Select
Application.Calculation = xlAutomatic
Application.ScreenUpdating = True
MsgBox Format(Timer - t, "0.0000")
End Sub

半百

For Each i In Selection
For Each i In Range([q2], lastcell)
也许 Selection你选择的区域只是一列（q列），而 Range([q2], lastcell)是a:q共17列的单元格，也就是下边的代码循环的次数可能是上边的17倍。