Getting into ContractIBeanIfc from another another document in Scripting

Hi Experts,

I am new to this, trying to get into ibean of agreement to set some default fields like effective date from another document like Rfx.

I approached like this. Under Rfx on save I got the agreement Uniquename then

Aghome =IBeanHomeLocator.lookup(session, com.sap.eso.api.contracts.ContractIBeanHomeIfc.sHOME_NAME);

doc1 = Aghome.findByUniqueDocName("xxxx");

Aghome.upgradeToEdit(oParentDoc1);

doc1.setxxxx(somedate);

parentHome.save(doc1);

not working as set method does exist only in ContractIBeanIfc.

can any expert suggest?