//Load event
        private void loadToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //create an open file dialog
            var loadFileDialog = new OpenFileDialog();

            //if the user selects a file and hits okay
            if (loadFileDialog.ShowDialog() == DialogResult.OK)
            {
                //Clear the spreadsheet
                ClearSpreadsheet();

                //create stream to load the file into
                Stream infile = new FileStream(loadFileDialog.FileName, FileMode.Open, FileAccess.Read);

                //load the file into the spreadsheet
                spreadsheet.Load(infile);

                //Close the stream so we can use it
                infile.Dispose();

                //Clear the undo and redo stacks
                undoRedo.ClearStacks();
            }

            //update the edit menu
            UpdateEditMenu();
        }