How do I keep a running total?

I hope I can explain this enough to get some help.

I want to keep track of the total amout of of a product in a month. I will be adding to this total a few times each month and taking away from the total each day. I need a cell I can reference from another sheet that will give me this total. Cells A1 thru A31 are the days of the month, Cells B1 thru B31 are the number used each day, Cells C1 thru C31 are the number added to the stock occasionally, Cells D1 thru D31 are the daily totals.
I need Cell D32 to equal the total on any given day of the month, this is the cell I will be referencing.
Can this be accomplished?

Thanks for any and all help.

Kenny

Kieran,
Here is a sample worksheet that I am working on.
What I would like to see is the total in Cell D35 to update with the total on any given day of the month. In my sample sheet the date is August the 11th and as each day passes there will be more items sold and possibly received. Cell D35 will keep track of this each day as the entered received and and sold items are updated daily.

Thanks for any help you can provide

Kenny

Davesexcel,
It looks like that does exactly what I need. Thanks so much, as always you guys have helped again.

Kenny