I have got a column of data like below:
Y
Y
Z
X
Z
X
Y
X

how could I use the excel function to make it becomes the following?
A B C D
1 Y X Y X
2 Y Z
3 Z X


The rule is,
1) once there is a change from X to Y / Y to X , new column will be applied.
2) Z will stick with the previous result in the same column

Please help cause I have so many data need to be proceed now