Calculate the number of options by divide current value by old values

I need to calculate the number of options, if there is a 1 in the column "start over?" you only buy one option. But

if there is a two in that column you divide the old option value by the new option value.

If the value is three you add up the old option values and divide it by the new option value

In the sheet it is more clear

I need to automise it for a large sheet.

Can someone help me please?