Calculate number of days on/off in a continuos work system per month - SUMIFS??

[M Frs]

Hello,

					off days <tbody> </tbody>	12
A	B	C	D		work days <tbody> </tbody>	30
Start	End	days	type
01/01/2015	12/01/2015	12	off
13/01/2015	11/02/2015	30	work
12/02/2015	23/02/2015	12	off
24/02/2015	25/03/2015	30	worl
	work	off
Jan	19	12
Febr	...	...
Mar	...	...
...

<tbody>
</tbody>

I need to calculate the on/off days of a continue work system within a particular month. The continue work system is 30 days working, and than you get 12 days off, but I need to bring that into months (Jan/Feb/...) while the work system exceeds the month end limits. The file needs to be flexible so that it can be also 30 days, 14 days or any other combination.
I have a column A with the start date, column B with the stop date after 30 days, than the next row, is the start date of the 12 days off, and in column the end date. Column C calculates the days (12 or 30) and column D gives the description on the work system (working or off), column D is in fact the same as column C. As you can see, I'm not a wizard in this things, so I hope I don't seem stupid asking the same kind of question, but the additional difficulty to the SUMIFS questions already answered on this website is that the # of days is a range, not 1 particular day. I actually don't know whether I will need to use SUMIFS or any other formula.

I don't know whether I could add the file to this forum, but it doesn't seems like.
Can someone assist me in the formula? In case I was not clear explaining my issue, please come back to me.

 

[M Frs]

Hi Everybody,

It seems to be a difficult request as nobody answered yet.
Can you have a look into this as I need it quite urgently? Or am I not clear enough?


Thanks