If I understand the question, you have:
PHP Code:
A B
1 xxx
xxx
xxx
xxx
2 xxx
3 xxx
xxx
xxx
And you want:
PHP Code:
A B
1 xxx
1 xxx
1 xxx
1 xxx
2 xxx
3 xxx
3 xxxx
3 xxxx
Insert a new column A. Make a1 = B1. Make a2 = '=IF(B2="",A1,B2)'. Copy A2 and paste into the rest of column a. Either hide B, or copy column a, do a paste special-> values into a new column, and delete a and b.