cannot bind or add elements because the node has no valid parent

I am getting following error when i am trying to add value to model node from value node :-

cannot bind or add elements because the node has no valid parent

Model Node has following structure :-

Zrfmc_Remarks_Input

|_Output

|_Output_IRemarks

I am trying to add value to Output_IRemrks node using following code :-

IPublicCreateCust.IOutputI_RemarksElement ele;

ele = wdContext.createOutputI_RemarksElement(new Ztmc_Remarks());

ele.setAppperson(wdContext.currentRemarksElement().getAppPerson());

wdContext.nodeOutputI_Remarks().addElement(ele);

I also tried using :-

wdContext.nodeZrfcmc_Remarks_Input().nodeOutput().nodeOutputI_Remarks().addElement(ele);

Can anyone suggest what i am doing wrong or proper code.

Regards,

Jigar Oza