Question: I need to ad the next sequence number in Column A automatically when I fill enter the next value in Column B. This sounds confused. Just see the snap so you will get the clear picture[![enter image description here](https://i.stack.imgur.com/91WEn.png)](https://i.stack.imgur.com/91WEn.png).

This should be done without usual dragging option. Is there any way

Answer: 
Make the Value of A1 equal to 1 and then from the A2 use the formula:

```
=IF(B3<>"",A2+1," ")

```

Drag this formula for the whole column.

In my solution I have a drag, but it is to define the formula for each of the fields. (I'm not sure if is this you are trying to avoid when you say 

> 
> without the usual dragging option
> 
> 
> 

)
You may achieve this using macros. Formula will increase the file size and processing time.

Right click on the sheet name on sheet tab-->select view code-->paste below code--> save file as macro enabled workbook.

```
Private Sub Worksheet_Change(ByVal Target As Range)

On Error GoTo step
If Target.Column = 2 And Target.Value <> "" Then
Target.Offset(0, -1) = Target.Row - 1
End If

Exit Sub

step:
Exit Sub

End Sub

```