Passwing parameter to CObol and vice-versa

Hi,
My program is calling a Cobol program. Now I have to pass a variable to Cobol and after some modification, some value has to be passed back to Natural program from Cobol.

Is it working the same way we use CALLNAT or any other things I need to taka care?

How can I pass it back to Natural program from Cobol.

Thanks,
Mishra

http://techcommunity.softwareag.com/ecosystem/documentation/natural/nat424mf/sm/call.htm