Rollover Budget with negative numbers by category

Hi!

I have a categorized budget:

Original Budget
category 1 - $100
cat 2 - $200
cat 3 - $300
Total budget - $600

If I spend $200 in category 1, therefore overbudget by $100, how can I create a formula to reduce all other categories proportionately? See below:

Adjusted Budget
category 1 - $83.33
cat 2 - $167.67
cat 3 - $250
Total budget - $600

Proportional Adjustment (PA) = 100/600 i.e (200-100)/600 = 16.66% (or 0.16666)

Adjusted budgets = Original value of category * (1-PA)