//Calculate sum label
	    	final CLabel sumLabel = new CLabel(group, SWT.RIGHT);
	    	sumLabel.setText("Sum: ");

//... Continued (button here etc.) ... then:
	    	
	    	calcButton.addSelectionListener(new SelectionListener(){


				@Override
				public void widgetDefaultSelected(SelectionEvent e) {
				}

				@Override
				public void widgetSelected(SelectionEvent e) {
					int index = array.getTopIndex();
					int sum = 0;
					while (index < array.getItemCount()) {
						String data = array.getItem(index).getText(3);
						sum += new Integer(data!=""?new Integer(data):0);
						index++;
					}
					sumLabel.setText("Sum: "+sum);
					sumLabel.pack();	
				}
	    		
	    	});