Making The Same Drop Down Box Display Different Sets Of Choices

I am making a program that needs some macro but I don't know much about it. There are a couple of things I am trying to accomplish and I'm supposing it would be easier to let you look at the actual program so I uploaded it.

In the drop down boxes in column C there are trucking companies listed. Each trucking company has different trucks with different numbers that pull different numbered trailers. When I select say, "T & L" from list c8 I need the lists in that row E8 & G8 to display only the information related to that trucking company and no others (as opposed to every trailer number and truck number on the lists in row 100). Only T&L drives a truck with the number 08 pulling a trailer with the number 564, etc. I need the same thing to happen for the truck list E8. When a particular truck is selected the lists in g8 narrow to the numbers of the trailers that that truck have pulled in before. So e8 (truck number 88) makes g8 list trailers 8855 and 8445 because that driver only pulls those trailers.

If you can kindly help me with that macro to work for a sheets in the workbook that would help a lot. The only thing is it's useless unless the program can learn new trucking company names with their respective trailers and trucks (we get new ones sometimes). I created the "ADD" sheet to be able to add new trucks, trailers, carriers (companies) and employees. If c8 doesn't have say "t&L" trucking company in it I can go to the add tab and type into cell a4 the carrier, d4 trailer number, g4 truck number, etc. I need that information to add itself to my list on the "page 1" tab into the orange colored list a100:a200 while the trailer goes to e100 and truck c100. The above paragraphs macro would then be able to sort the data in the list when a carrier is selected.