我要实现给A列编号，如果B3不为空，则A3=1，否则A3=2，A4=3...... 但运行如下代码后不起任何作用，也不不报错，哪里不对啊？求指导，谢谢
Sub 编号()
Dim i%, d%
a = Application.WorksheetFunction.CountA(Range("O2:HG2"))
For d = 3 To rownum Step 1
For i = 1 To a - 1
If Cells(d, b) <> "" Then
   Cells(d, a) = 1
   Else
   Cells(d, a) = i+1
   End If
   Next i
 Next d
End Sub