Changing Cost Allocation Macro?

I am trying to write a Macro to allocate a certain cost across thousands of orders. The number of orders will obviously change monthly. The cost is relatively small, and when divided evenly by the total orders needs to be rounded up to the nearest cent (Typically $.01 - $.02)

I then need the cost to be insered in a colum running next to a total cost column, but I need it to stop when it reaches the total cost and just start adding zeros to the rest of the orders so as not to overcharge.

Not sure if I need to incorporate solver somehow. I figured I would reference the allocated cost from a cell in the worksheet but not sure how to insert any algebraic logic into a macro.