This is not an easy question to answer, and the solution is far too complex to deal with in a little textbox like this one.
However, it is a problem that we do see a lot - it's the same problem that sales guys used to have before mobile internet - and there is a solution. It's called
and I'm afraid it is not as simple as "write this" - you have a fair amount of reading to do.
Start here: https://www.google.co.uk/search?q=SQL+Replication&oq=SQL+Replication&sourceid=chrome&ie=UTF-8
] and follow a few of the links - they will give you an overview and you can start designing your solution from there.