How to automate available options from a user selection

Hi all
I am trying to put together a product code / description generator
I am using the drop down lists to help with this but would like some more automation if possible

i would like it so that when a user selects an option from the first drop down list
the next thing that happens is that all options not relivant to this selection are blanked out !

so for example if i run a factory building both cars and motorbikes
The users first task is to select "cars" from a drop down to produce a product description for a new model of car
In doing this the aspects that specificaly relate to motorbikes e.g. handlebars are no longer available.
this way the user can't possible create a description that doesn't make sence, but info for both products are on the same spreadsheet.
This is important because some of the criteria overlap - e.g. they both have wheels

hope that paints a picture of what i am looking for
any help appreciated
many thanks