Dynamics CRM 2013:Get/Set Business Process stage field value.

Xrm.Page.getControl("header_process_fieldname").getAttribute().setValue(value);  //Set Value

Xrm.Page.getControl("header_process_fieldname").getAttribute().getValue();  //Get Value

 //****** get the Id of business process Satge*******************************

    var StageId = Xrm.Page.getAttribute("stageid").getValue();

    

    if (StageId == "7f5247fe-cfc3-42bc-aa77-b1d836d9b7c0") {

        var Control = Xrm.Page.getControl("header_process_fieldname").getAttribute();

//fire onChange event.

        Control.addOnChange(FunctionName);

    }