Make sum of all cells equal certain value

Hi,
First off, I'm sorry for the vague title, and/or if there is another thread on here explaining the answer. for some reason, I cannot think of how to phrase what I am looking to do.

Let's say there are 3 cells A1:A3 and each cell is B1 divided by 3.

Unfortunately, B1 is 10, so the cell value for A1:A3 is 3.3333.

what I am looking to do are 2 things
1) have the sum of all cells equal B1 (10 in this case)
2)make each number an integer.

so, an example might look like
a1 = 4
a2 = 3
A3 = 3

Is there a way to do this with a formula?

Basically, I am just trying to create a shipping schedule for a lot of different parts, given a yearly quantity. so all shipments have to be whole numbers and the sum of all shipments must equal the yearly quantity.

any ideas?

Yes!!! have one of the cells be the difference between the sum of all three divided by B1 and the truncated value of the other two

c1 : sum(a1:a3)/b1-sum(c2:c3)
c2 : round.down(a2/b1,0)
c3 : round.down(a3/b1,0)

that's a good idea and I think it will work.

thanks!