count values in a column, but only if the value does not appear in the previous cells

Hi,

Im trying to count values in a column, but only if the value does not appear in the previous cells in the row

eg... Count the YES's

acc Y Y N Y
Pro N Y Y N
tim N N N Y
rac Y N N Y

Existing 0 1 1 2
New 2 1 0 1

Please can you help?