Determining partners in a transaction?

Hello Experts,

I am new to CRM. I have a requirement in PDP. There are 4  function that is SOLD TO PARTY,SHIP TO PARTY,CONTACT PERSON and PAYER is used in a sales order document.When end user enter sold to party 's id,it is determining other partner function.This is the general scenario which I got it how to do.But now end user requirement is  that when he enter the contact person id then also the all function should be determine.Likewise when he enters ship to party's id then also all other partner have to determine.

So can you just guide me how to do this thing...? Is it possible to this thing with standard SAP behavior or needs any enhancement?