Schema determination in sales order for external services

Hi,

I've created a maintenance order including two services into operation 10

(control key PM03). The pricing log in the order shows that the system

uses schema ZS0001. After releasing it, the purchase requisition (class

ZMS1) is created. When the PO is created (class ZMS2) via requisition

assignment list (ME58), the schema is changed to RM0000, despite of the

fact that table T165A contains the following entries:

Doc cat. Doc Type Procedure

B ZMS1 ZS0001

B ZMS2 ZS0001

F ZMS1 ZS0001

F ZMS2 ZS0001

I would need to keep the schema to ZS0001 in the sales order to perform

the right price determination.

Any help? Many thanks.