Calculate Hours within a month

Hi

I am trying to calculate the numbers of hours between 2 dates but that lay within a specific month. The dates may cover some, none, or partial part of the month. I have the below formula for a year, but am struggling to convert it to months. Below formula (C is start date), (D is end date), G2 is the year ie 2012.

IF(AND(YEAR($C4)=G$3,YEAR($D4)=G$3),$D4-$C4,IF(AND(YEAR($C4)=G$3,YEAR($D4)>G$3),DATE(G$3,12,31)-$C4,IF(AND(YEAR($D4)=G$3,YEAR($C4)<G$3),$D4-DATE(G$3,1,1)+1,IF(AND(YEAR($D4)>G$3,YEAR($C4)<G$3),365,0))))

Example of my issue ie I want the number of hours in Feb 2016:

start End
01/02/2016 01/03/2016
01/02/2016 02/02/2016
01/01/2016 05/01/2016
01/01/2015 01/04/2016
01/04/2016 01/10/2016

I can get the numbers of hours between the dates, but as you can see this isn't relevant as some/non/all of the time period may fall in February.

Any help would be much appreciated.

Kind regards

Adrian