need help to create add-on for Inter company transaction

Hello Experts,

I want to create one add-on for inter company transaction. I need your help in it.

Scenario:

There are two company databases A and B.

If user creates Sales order in Company A, add-on or any procedure should create respective Purchase Order into Company B at a same time.

Question:

1. Is it possible to create an add-on which can post document into another company?

2. Can we create an external windows service application which can trigger at some specific timings and generate POs into company B on some specific criteria on SOs creation in company A?

3. Is there any other suggestion available to achieve this requirement?

Thanks in advance.

Regards,

Amit Patel.