BaDi for checking RFQ (ME41, ME42)

Hello,

the short version of my question is simply in the subject: is there a BaDi for checking a RfQ before saving?

Given that Purchase Order & Purchase Requisition have one (ME_PROCESS_REQ_CUST, ME_PROCESS_PO) I would think so, but I can't find either by looking on System (a S4H) or by Googling.

Something more about my requirements: I was asked to put some business data checks on RFQs, by implementing ME_PURCHDOC_POSTED; something about checking vendor number, materials used...this kind of things.

This BaDi has only one method (POSTED), and the documentation looks clear to me:

With the Business Add-In (BAdI) ME_PURCHDOC_POSTED, you can trigger a variety of follow-on processing operations for purchase orders, contracts, RFQs, and quotations at the time of posting.

There are a couple things that do not work:

• After triggering a 'E' message, line items cannot be edited any more: they are output-only
• I have been asked to check RFQ q.ty against P.Req q.ty; yes, I can do it, but even if I raise an error, user cannot change the q.ty amounts: they are output only

I kind of suspect that this is because this BaDI is used on follow-on processing operations, but I'm having a hard time explaining this. If I can't find a BaDi or an exit to put my checks in, I'll probably have to look into moving the checks in implicit enhancement points BEFORE saving...but really, it seems weird to me that SAP hasn't provided a way for customers to implement additional checks in RFQs.

Thanks in advance