Calling a BAPI in CAF

Hi Experts,

I have to populate a column in a table with the values fetched from a BAPI. The procedure we have to follow is

1)Webdynpro dc will call CAS through a model

2)CAS will call BAPI.

Can any one help me in developing the senario.I am completly new to CAS.

Thanks,

Khyana Prabha