auto numbering in previous cell based on enter adjacent cell using target cell

[Hasson]

Hello
I have headers in row10 and data starts from row11. I want when entering data in column B , then should autonumbering in column A 1,2,3 ....
just when fill in cell for column B then should fill in previous cell in column B using target range by sheet module .
thanks

 

[Hasson]

What I mean press when double click in the cell and don't write any thing then will write number in column A why?

 

[My Aswer Is This]

What I mean press when double click in the cell and don't write any thing then will write number in column A why?

Not sure what you're now asking about.
We never mentioned double clicking before.

 

[Peter_SSs]

See if this does what you want

Private Sub Worksheet_Change(ByVal Target As Range)
  With Target
    If .CountLarge = 1 And .Column = 2 And .Row > 10 Then
      If Len(.Value) > 0 Then .Offset(, -1).Value = Val(.Offset(-1, -1).Value) + 1
    End If
  End With
End Sub

 

[Hasson]

We never mentioned double clicking before.

yes , but you told me you don't understand my , that's why I said double click .
any way thank you and @Peter_SSs have solved it .

 

[Hasson]

@Peter_SSs
yes , this is what I'm talking about .
thank you so much .

 

[Peter_SSs]

You're welcome. Thanks for the confirmation.