Thanks VW, Great piece of Maths there! ....but I don't think i explained myself properly...
The idea is that I need to add new conditions to the script, I need about 50 conditions in all based on any random combination, hence having to declare the condition for each drop-down option.
option 6 might be: 1-block, 2 - none, 3 - block/
option 7: 1-block, 2 -none, 3 -none
option 8: 1-block, 2-block, 3-block