Autofill/lookup in macro

I have a dropdown box with order numbers in a cell, well cells as i have multiple customers each with orders in their own drop down box. On another sheet i have a table with the orders for every customer with the order number and the details about that order (say item, quantity etc)

What i would like is that when i choose one of the numbers in the drop down box it autofills the columns to the right with the data. So i'm guessing this would be some kind of lookup in a macro that activates when whats in the cell changes, but i dont know what the code would be. Can anyone help?

Also for the main page where the drop downs are, in the columns for the details are more drop downs where if the order is not existing the details can be put in manually. Would having a macro for this purpose affect having those drop downs?

Any help will be appreciated. If my explanations are off then i can provide more info and i can attach a cutdown version of the spreadsheet if that helps.

I've uploaded an example of the spreadsheet to help.

When you look at it for the 2 customers there is a sheet with their orders on (well order), and on the main sheet there is a column where you can select the order number. Each customer can only have a max of 6 orders so the order numbers are just 1 to 6 for each customer.

So yeah what i'd like is for you to be able to choose say order 1 for customer 1 and it autofill the columns with whats on that order sheet. So i'm guessing it'll have to look for both the customer and the order number then autfill it somehow. But i dont want it to remove the ability to choose it yourself if there are slight changes to the order.

I hope someone can help, thanks