Blanket or run down type purchase order

Evening All,

I know I'll be asked to post this as an idea (which I will do)

But wondering has anyone come across a facility or addon for Sage 200, where you can create a blanket or run down Purchase Order.

Basically this would he used where a contract is in place and a fee is set/agreed for the year, but without having to go through the whole GRN process,  to be able to post invoices against the PO and run the overall agreed value down, so when the value is reached or depleted the PO will compete and not allow any more invoices to be posted.

I can see there is a blanket type PO in Sage 300 and I believe this functionality is also available in SAP.

Would be great to hear if anyone has come across this scenario and wa able to work around it.

Thanks in advance.

Paul