Changing the Smartform in SRM Offline approval

Dear SRM Gurus,

We are using SRM5.0 (exteded classic scenario). We are using offline approval process. The approval process is working fine, user is receiving a mail and layout of the business object as an attachment. User is receiving standard smartform layout with SAP logo, but we have to change the standard smartform with customised one.

But in the standard class <b>CL_BBP_MESSAGE_CREATE_OFFAPP</b> in the method <b>DETERMINE_FORM_AND_PARAMS</b> the layout names are hardcoded. Is there any BAdI or any other process to change the layout name.

We have also implemented BAdI <b>BBP_OFFLINE_APP_BADI</b> for the method <b>DETERMINE_CLASS_NAME</b> to pass our own class (copy of class <b>CL_BBP_MESSAGE_CREATE_OFFAPP</b>), then there is an ABAP dump saying <b>'Type conflict when assigning object references'</b>.

So Please suggest the appropriate solution.

Thanks in Advance,

Chandra Sekhar.