User form with combo/option box dependencies

I have been trying to build a userform which utilizes combo boxes and option boxes to fill in further dependencies. I have gotten some great help but now I am afraid that my model has changed and I am stuck.

I am trying to have a form which allows the selection of 1 of 3 brands by way of option boxes. By choosing a brand will affect the further dependencies. The next selection will be option boxes to select the type of error, (two options) which will further affect the further dependencies. The next will be a combo box that list available possibilities based on the first two selections. This selection will then affect the next combo box. Selection of the next combo box will then code the transaction accordingly.

I feel my code is all screwed up for the combo box. Also my thought process was to have a table for each possibility but am not sure if that i s the best method.

I am enclosing an example of the layout, but am not sure if I am in the right direction or not.

ANy help would be greatly appreciated.