Conditionally fill the cell!!

[ckmoied]

Cell A1=1, A2=A1+1, A3=A2+1 and so on
However I want the cells in col A to show their respective values only if the corresponding cells in col B have some values.

So

A1=1 if B1=Something
A2=Empty, if B2=Empty
A3=3 if B3=Something, and similarly
A4=Empty, if B4=Empty

Please suggest a function to accomplish this task.

 

[Andrew Poulsom]

Try:

=IF(ISBLANK(B1),"",ROW())