Hi Aisf,
I would suggest to create a custom table and publish its page as web service. Insert your relevant data using api call.
Then make a code-unit to handle the posting as an extension after validating the relevant data in your custom table . Finally schedule it in a job queue.
Now when you enter the data in your custom table using page api service, the scheduled job will take care of it and post the entery using journal (the logic you have written in your code-unit)
Hope it will work for you. I would suggest to handle posting routine from inside Business Central.
