Update Total and the numbers that make up that number update also.

Ok, so here's my problem.

I work at an accounting company, every month the accountants have to enter certain fixed expenses and provisions to the system. However, the totals assigned to each account can change. Imagine this:

Cost center 1: $50
Cost center 2: $50
Cost center 3: $100
Cost center 4: $50
Cost center 5: $100
Cost center 6: $50

Provision: $400


So, evidently the $400 is the total sum of the 6 amounts assigned to each cost center, as a percentage. So for example, CC 1,2,4 and 6 has 12.5% and cost center 3 and 5 have 25% assigned.

How can I, by changing the total ($400), update the cells above.

So imagine $400 gets doubled to $800, I want the same percentages assigned but the amounts to change.

Thanks and I hope you can help me, I know it's probably easy. I also have A LOT of accounts and cost centers...