dependant comboboxes picking up wrong items

hi
my comboboxes are picking up items from another row,have been trying to find out why and are stumped,if you select frmmain ,location as 200 and plant as e206
it shows 5 instances of e205 but shows one on 200 unit as should be,enter workshop and e206 and says there are 4 instances at workshop but also shows one at w/bay,enter w/bay and it shows all 4 again from workshops,i am completely at a loss to why all info on sheet correct,any ideas anyone please
cheers colin