Round UP Formula for TIME

Hi All. I need an excel macro to populate a cell with a time slot based on the previous column which is a datetime value. e.g.
if column A is 1-Apr-2014 1:57 PM, column B will show time slot as 2:00 PM,
if column A is 1-Apr-2014 11:15 AM, column B will show time slot as 12:00 PM,
if column A is 1-Apr-2014 3:25 PM, column B will show time slot as 4:00 PM
and so on and so forth.

Please guide on this. Thanks in advance.