计算包含数据的列中的单元格数

I have this code:

我有这个代码:

Dim first As Integer
Dim Last As Integer
Dim i As Integer

For i = 1 To 17
    first = (ActiveCell.Row + 1)
    Selection.End(xlDown).Select
    Last = (ActiveCell.Row - 1)
    Range("J" & first & ":J" & Last).Select
    Selection.Value = "=J$" & (first - 1)
    Range("A" & Last + 1).Select
Next i
Dim first As Inte