Calculating monthly sales goals based on growth to target?

Hello,

I have included an image of what I have so far. Basically, I want to be able to keep the total goal (D17) at $1,000,000, and have the goals for the months (D4-15) always add up to that one million goal, but change based on the Actual column (F4-15). For instance, if one month is $5,000 short, it adds that $5,000 evenly to the remaining months but still adds up to 1,000,000. I understand that adding to the goal column would make the sum go up and it needs to be a static 1,000,000, but I want to find a way so when I input the actual sales, it edits the remaining goals to reflect over/under previous months' goals. Is that possible?

The only "solution" I have now is to add the difference of last month's goal and actual sales to this month (For instance, D6 is 74045+(D5-F5) to add what we were short in Feb to March). However, it only adds the rolling deficit to the next month instead of spreading it out to still equal 1 million growth from this month.