Payment to Vendor Based on Payment Term

Hi experts,

I want to create some new payment terms in SAP with integration with IV. Say if I have 30 days credit period in PO payment term , system will not allow to pay vendor before 30 days of GR date.

How to customise this. Can any body explain the process step by step? Is it a config issue or customisation issue? If need to write code, where to write it.