Sequence number in excel for non blank rows
<p>How to add sequence numbers in excel, wherein the sequence number starts based on the value of the column B. It should not add the sequence if there is no text in the corresponding row of Column B.
So the row 4 should start with 1 since the column B is having some value.</p>

<p>The example sheet is attached.
Also how can i auto update the sequence if i add new row to it.
<a href="https://i.stack.imgur.com/b7Jb1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/b7Jb1.png" alt="enter image description here"></a></p>