Problem excel with sum

Hy,
I want to do some SUM calculation for some barrels that are not full enough.

Let's say I have some barrels that are filled differently (50% or 100%) every day. If in two days I am filled with 2x50% (which means that I filled the barrel from the previous day) I wish that in one way or another they make the total amount of barrels of 100%, this 2x50% to be calculated as a single barrel.

The problem is that I need and the amount of barrels that are filled only 50%.

exemple>If in three days come 5x100% 3x50% and I would like drums amount of 50% to be 1 and the 100% to be 5. Somehow or another 2x50% to be calculated for each 100% and do not take into account these two in the amount of 50%.

@Edit

Data	     nr. Crt	   x%	
16.11.2013	17	100%	
16.11.2013	1	50%	
17.11.2013	1	50%	
17.11.2013	5	100%	
18.11.2013	3	100%	
18.11.2013	1	50%	
			
	Amount		
50%	3		
100%	25		
			
I would like to be displayed the following calculation for the amount			
			
50%	1	2 of the 50% to be considered as one of 100%	
100%	26