Moving Data Down one, Left one based on data in same row, different column

I have:

Col A----Col B----Col C
row1 cow cat
row2 dog
row3 sheep

I need:

For all rows, if Col B has data but Col C does not, move data from Col B into Col A and down one row

Col A----Col B----Col C
row1 cow cat
row2
row3 dog
row4 sheep

duplicate post.

http://www.excelforum.com/excel-prog...nt-column.html