Substitution exit

Hello,

Is there is anyway of passing the data from standard code to an user exit without changing the standard code.

I have the contents inside an internal table (it_partner) which is part of standard code (CJ20N). Now I need to pass the contents (it_partner) to an userexit.

Will substitution exit help me in this case?

If not is there any other way of achieving this without copy the standard code?

Thnx.