New at DTL. I need some pointers on this DTL

For all Prosthetics orders:
when ORC-1(Order Control) is "NW" (New Order), need to update OBR-18(Placer Field 1) based on PV1-2 (Patient Class) value.
assumption is that the selection logic is that all prosthetics orders with OBR-18 field is always blank.
Description :
If PV1-2 is I, insert I in OBR-18
If PV1-2 is O, insert O in OBR-18
If PV1-2 is E, insert O in OBR-18
If PV1-2 is P, insert O in OBR-18
If PV1-2 is R, insert O in OBR-18
If PV1-2 is B, insert O in OBR-18