Loop to copy cells based on content from other cells

Hello,

I would like to be able to fill cells with a date value based on data within a sheet. In column A, I need to fill rows of dates based on the last date entered and also based on the time, which is in column B.

For example

A B
05/02/14 07:00
08:00
09:00
.
.
.
00:00
01:00


I need to populate the rest of column A with "05/02/14" until I reach "00:00". I would then change the date to 06/02/14 (or date +1). I can not quite workout how to:

1) count the rows in column A which are blank relative to column B
2) Copy and paste the date up until 23:00 and then change it to the next day at 00:00.

Any help would be much appreciated!

Thanks

James