I've read the article that there is no support in the C167 KEIL compiler. Hence, I've tried to use MACRO assembler as follows. *DEFINE ( calls(Rx, Ry) ) LOCAL RETURN_LBL ( MOV R13, #SOF %RETURN_LBL MOV [-R0], R13 MOV #%Rx, #SEG %RETURN_LBL MOV [-R0], R13 JMPS SEG #%Rx, SOF #%Ry RETURN_LBL: ) I have no translate error. However, it doesn't work. Is it possible to define an operation to another set of operations?