How to tackle this? (ommisions/differences between two Excel columns)

I use some dispatch software to have a 'common interface' for handling/dispatching sales from three sales channels - Ebay, Amazon & my own website - it works well.

I also have Amazon dispatch stuff for me (fulfilled by Amazon ...or FBA for short)...that works well.

the problem is my dispatch software is still meant to get all the Amazon FBA orders (not that I have to do anything, but just so I've a record)...alas, it seems my dispatch software is only recording about 30% of the transactions for Amazon FBA orders.

i therefore need to trap all Amazon FBA orders that my dispatch software doesn't know about.

I can export all the Amazon FBA orders from my dispatch software...I can also generate a report from Amazon of all Amazon FBA orders they have sent out.

what I need is a way of comparing two columns column 'A' could my dispatch software's known 'Amazon FBA' orders (i.e. so this info will have missing order) & column 'B' could be the orders as pulled from Amazon (which will be definitive)

i need a macro to go down the Amazon column 'B', & highlight any orders that are missing from column 'A', therefore logic like this

select Column 'B' first cell
If the same number is exists anywhere in colmn 'A' all is well...move down one cell...rinse repeat
If the same number doesnt exist in colmn A...then highight the present cell in column B (eg red bolded text etc) & move down one cell...rinse repeat

therefore after completion I should have a lot of highlighted cells in column 'B' (these are Amazon FBA orders that my dispatch software hasn't got)

Any ideas, leads, top tips?