How to Create Sales Order in Other Company Database

Hi everyone,

I am using SAP 9.0.I have a issue as follows.

Customer has two companies.These two companies has interlinked transactions.

Let us take an example

companies :Company A

                   Company B

Issue          : If the Company A has Purchase order then Company B has Sales order.

customer wants to automate this process.How can do this by using SDK?

Please suggest me.

Thanks and Regards

DEV