BAPI_ACC_GL_POSTING_REV_POST

I want to use the bapi BAPI_ACC_GL_POSTING_REV_POST for reverse the document line items and how can i reverse the document line items with in the system means i am not calling this bapi from outside but inside, i need to reverse the entries.

if possible means, what can i do for the parameters OBJ_SYS,OBJ_KEY,OBJ_TYPE.

Thanks in advance.