Excel 2007 : If date.... Help

HI, I am new to the forum, and have some problem wiht a function:

I need to extract the month out of a date, but with the following catch, id the day on the date is the 15th or less, it must show the correspoding month, if the day on the month is 16th or more, it must show the following month, like this:
DATE Result:
12/01/2011 January
18/01/2011 February

Can Anybody please help????

Thank you