special procument type & PR type

hi experts,

I got a problem now, and needs your help.

As show below, the procument type is 'F' and the special procument type is '30', after run MD02, a PR has been created, PR type:NB;

I want to achieve the propose that the material with special procument type '30' creates the NBWX purchase requsition, while the material with special procument type = ' ' creates NB purchase requsition.

I don't know where to config it.

please help, thanks.