DataGrid CellEditEnding event to command. How to pass in DataGridCellEditEndingEventArgs 'e'? MVVM

Question

So i've got my command working, except for the fact that I'm not getting the DataGridCellEditEndingEventArgs 'e' passed down to me... this is my xaml in the datagrid

                                    <i:Interaction.Triggers>
                                        <i:EventTrigger EventName="CellEditEnding">
                                            <i:InvokeCommandAction Command="{Binding RelativeSource=
                    {RelativeSource FindAncestor, AncestorType={x:Type Window}}, Path=DataContext.MainWindowViewModel.ObjDataGrid_CellEditEnding}"/>
                                        </i:EventTrigger>
                                    </i:Interaction.Triggers>

And my test command

    private ICommand objDataGridCellEditEnding;
    public ICommand ObjDataGrid_CellEditEnding
    {
        get
        {
            if (objDataGridCellEditEnding== null)
            {
                objDataGridCellEditEnding= new RelayCommand(CellEditEndingTest);
            }
            return objDataGridCellEditEnding;
        }
    }

    private void CellEditEndingTest(object param)
    {

    }

param is always null.... and I don't know why...

Any help would be appreciated...

Where e is needed

        if (e.EditAction == DataGridEditAction.Commit)
        {
            TextBox cellTextEdit = e.EditingElement as TextBox;