public void onClick(ClickEvent event) {
try {
int row = Integer.parseInt(rowBox.getText());
int cell = Integer.parseInt(cellBox.getText());
FlexTable headerTable = ScrollTableDemo.get().getHeaderTable();
headerTable.insertCell(row, cell);
headerTable.setHTML(row, 0, " ");
} catch (NumberFormatException e) {
Window.alert("Please enter valid integers for the row and column.");
} catch (IndexOutOfBoundsException e) {
Window.alert("The row or column index you entered is out of bounds.");