Copy value from previous row

[RAJAPPA]

Fill the blank field with the one just above it
A csv file like this
A ,b ,c ,d
1,2,3,4
, 5,9,7
, 9,8,0
2,8,5,4
, 9,5,0
, 9,7,1

Pl note 3,4,5,6 is blank
It should be filled with
1
1
2
2
2
Thanks in advance

[Neil Butterworth]

There is currently no way of doing this, though it's an interesting idea.