Look the content in the spoiler in my first post here. There has a solution with an example how to use it...
You'll need change the range of rand from '100' to '10000'.
Rate (1 = 0.01%, 10 = 0.10%, 100 = 1.00%, 1000 = 10.00%, 10000 = 100.00%)
And change the 'if' from:
if (.chance >= 1 && .chance <= 5){
To:
if (rand(10000) < .chance){
And change the value of variable '.chance' to the rate you want:
From:
set .chance, rand(100);
To:
set .chance, 500; // 500 = 5.00%