How to change weekly growth rate of neutral stacks ?

[bonecollector]

Topic says it all kinda. How to change the growthrate / growthrate function of neutral stacks (on random maps) ?

Alrdy checked the 57 script, but sadly it only adjusts a static number to neutral stacks at start. And my erm skills are like non existent yet. Since i like to play large random maps i rather like to keep the stacksizes at beginning of the game as it is but have (much) bigger stacks after game continued (eg at end of 2. month).
Something like a free definable growh-function that starts slowly but raises non linear.

As i understand it, it needs a script that not done by post instruction trigger but runs always after the normal growth of stacks is done