Problem with executing bapi with structured input parameter

Hi Experts,

My RFC module requires input in form of a data structure.

So I my creating a model object for the structured input parameter . but he setter method requires arguement as abstraction list.What does it mean?

Zdata_Input getNewdata = new Zdata_Input();

wdContext.Zdata_Input().bind(getNewdata);

Zsubdata NewNo = new Zsubdata();

getNewdata.setZsubdata(NewNo); // giving Error

Zdata_input is my main context node .

Zsubdata is subnode of this model node .(Table Parameter in associated BAPI) .

Thanks in advance .