Can I make this conditional formating list remove words i've already used?

[tonywatsonhelp]

Hi Everyone,
I have a reather complex formula that I put in conditional cormating so I can have a dependent drop down list,
the formula is this
"=OFFSET('Attribute Dropdowns'!$H$2,1,MATCH($G9,'Attribute Dropdowns'!$H$2:$Z$2,0)-1,COUNTA(OFFSET('Attribute Dropdowns'!$H$2,1,MATCH($G9,'Attribute Dropdowns'!$H$2:$Z$2,0)-1,500,1)),1)"

What it does is creates a dropdown list using data in the range Attribute Dropdowns'!$H$2:$Z$last row, it finds the coulmn to use ny looking at the word in G9, and matching it with the headers in Attribute Dropdowns'!$H$2:$Z$2
this all works great, except as i go down the page, i can get duplicates as the dropdown does not adjust,
lets say this code was in H9, is there a way to make the same dropdown list in H10 but exclude the word in H9, i've tried adding in a filter to the formula but conditional formating wont let it work,

not sure how easy that was to follow but if anyone has any ideas how i can sort this out it would be great

thanks
Tony