F110 : How to group payments by assignement field (ZUONR)

Hi,

I have created a Grouping key '02' and I assigned this grouping key to a vendor for which I will run a payment program.

In customizing I assigned field1 ZUONR (Assignement) to my Grouping key '02'

I run Tcode F110 to pay 3 invoices :

Invoice 1 : Assignement = Investment

Invoice 2 : Assignement = Exploitation

Invoice 3 : Assignement = Exploitation

When I run a payment program (F110) the system create one Payment document and one Check for the 3 invoices !

However, for my case I want to create 2 payment documents and 2 Checks, one for invoice 1, an other for invoice 2 and invoice 3

Please Have I forget a Customizing point ? how to do to have 2 payment documents in my case ?

Regards.