You can use the 'Error Board' to see what errors are present.
Here are some (rough) samples to give you an idea of how to get to the board.

function CTRL4_5::OnClick(eventObj)
{
    // Error Count
    XDocument.UI.Alert(XDocument.Errors.Count);
}

function CTRL5_5::OnClick(eventObj)
{
    // Show Error Msg #1
    if (XDocument.Errors.Count > 0)
        XDocument.UI.Alert(XDocument.Error(0).ShortErrorMessage);
}

function CTRL7_5::OnClick(eventObj)
{
    // Add Error Msg #1
    XDocument.Errors.Add(xmlDataFld1, Empty, "Msg 1", "Long Msg 1", 1);
}

function CTRL10_5::OnClick(eventObj)
{
    // Delete All Ctrl #1 errors
    XDocument.Errors.Delete(xmlDataFld1, Empty);
}

function CTRL11_5::OnClick(eventObj)
{
    // Delete all errors
    XDocument.Errors.DeleteAll();
}