problem deleting last cell in a specific row

hey everyone

i'm using a table like this one :

A B C D

1 Main | value | value | value
2 Extra | value | value | value
3 Main | value | value | value
.
.
n Extra | value | value | value

i want to delete every cell in column "D" only when cell in column "A" contains "Extra" value.

help plz
regards