How to find the Next Doc Number?

I will automate the creation of "picking" in deliveries in an interface. Usually the picking is created on the delivery manually, and SAP assigns that picking document the next number.

How can I get the next number when I create picking in the interface?

I need this as a parameter in SD_DOCUMENT_UPDATE_PICKING, it asks for the subsequent doc number. I can put anything in there, but want to create the new Picking Doc number just like the system would do it.

Thank-You