Random count/number for vending machine.

Hi guys.

I am struggelig a bit with a challingig pogram, hope to have your input an ideas.

I am making a new controlling system for a vending machine. i Am using a logo 8.3 with extra 4 outputs (in total 8)  Each output has been setup to the number pad on the machine that means:
Q1 = 1, Q2= 2, Q3= 3 ... And so far up to 8.

The idea is that when you have put money in the machine you press 1 button ( I1 )  And the logo push a totally random generated number. (
Example  I1 activate - small delay Q1 ON/OFF - small delay Q4 ON/OFF .
So now the machine will give you the product placed on number 14.

The machine has 5 lines with 8 rows.  So the first number to picked can NOT be Q6-Q7-Q8 since we only have 5 lines.

So far so good, i got that to work. :)

Now i have added counters that i am going to use in LWE so i can see how many products that are back in each shelf. Counters start at 8 and count down 1 every time logo trigs each number.

And now to the problem:

- If for example 58 (Q5 + Q8) has been selected 8 times, then the counts go to 0 and i want the logo to NOT pick that number anymore, but somehow i cant find a solution that works for that...

The whole pogram is actually based on the Random generator module, but maybe there is a more simple solution... I2 is a sensor that detects when the product falls down and I3 was ment for a reset when the machine has been filled up and all counters go back to their start point.

Hope you guys maybe have a solution and it make sense.
attached is the pogram and a picture where i have added some numbers to make it clear for you.