Add as below:
void clicked()
{
FormRun formRun;
Args args;
args = new args();
args.record(MyTableParent);//Added this
args.parm(MyTableParent_MyID.text()); //from a datafield in Form A - Datasource sA.
args.name(formStr(MyFormChild));
formRun=ClassFactory.formRunClass(args);
formrun.init();
formrun.run();
MyTableParent_ds.refresh();
MyTableParent_ds.executeQuery();
super();
}