It i my inderstanding that a sub grid may only be load by and “XML file” my question is can it be an XML string ?

While most simple way is to use separate XML file, component provides two events, which allows to change behavior and load sub-grid from any other source. … subrowsndd

Something similar to next can be used.

    subgrid.loadXMLString(data); // use the current data as configuration xml
    return false; // prevent default behavior