Changing exposed views options

Hi Everyone,

I have created a view with 3 choices which are exposed showing the contents.

Trade | Suffolk Town/City | Norfolk Town/City >APPLY

But as you can see this is not good as there is a conflict between Suffolk & Norfolk. If say I only wanted a trade company in Suffolk there is no None choice in Norfolk and my results would show whatever choice I made in Norfolk as well, I need either one or the other.

Below is what I would really like:

Trade | County | Town/City >Apply

If I choose an option in County (Suffolk/Norfolk) then this county is the one that shows in the Town/City dropdown option.

My PHP & MySql knowledge is at beginners level 0 so I would really appreciate it if someone could tell me how to do this in views if possible

Thanks Guys

Robert