How to check if the call is RFC or internally???

Hi,

There is one BAPI which is executed both internally and through RFC call.

I want to restrict some of the code in the BAPI if it is made through RFC call.

Is there any system variable which tell if it is RFC call??

I tried with function module "RFC_SYSTEM_INFO", but the problem with this FM is it will make a RFC call to the caller system to get the system attributes and I do not want this as it will impact performance.