How should I restrict invoicing before PGI?

Hi,

SAP is presently allowing me to generate invoice prior PGI is performed. Could you please guide how should I restrict this in copy control settings? Also, once invoice is generated before PGI, it triggers revenue generation too. I want to restrict this and bring in between a proforma invoice after delivery instead of invoice. What should I do? Will that stop revenue generation?

Thanks for your expert suggestion/comments.