public class OleExcel extends OleClientSite {


	public static final String ID = "ExcelSheet";
	private static final int CELL_VALUE_ID = 0x00000006;
	private static final int CELL_ID = 0x000000c5;
	private static final int SHEET_ID = 0x000001e5;
	private OleAutomation cell;


	public OleExcel(Composite parent, int style, File file	) {
		super(parent, style, file);

		OleAutomation workbook = new OleAutomation(this);
		OleAutomation worksheet = workbook.getProperty(SHEET_ID,
				new Variant[] { new Variant(1) }).getAutomation();

	
			cell = worksheet.getProperty(CELL_ID,new Variant[] { new Variant("A1") }).getAutomation();
			cell.setProperty(CELL_VALUE_ID, new Variant("Testeintrag"));
	}

}

	
...
@Override
	public void createPartControl(Composite parent) {

		try {

			try {
				OleFrame frame = new OleFrame(parent, SWT.NONE);
				site = new OleClientSite(frame, SWT.NONE, "Excel.Sheet");
			
			
				//get an Excel workbook       
			     OleAutomation workbook = new OleAutomation(site); 

			     // activeSheet
			     int [] ids = workbook.getIDsOfNames(new String[]{"ActiveSheet"});


			
			} catch (SWTError e) {
				System.out.println("Unable to open activeX control");
				return;
			}

	
			
		} catch (SWTError e) {
			System.out.println("Unable to open activeX control");
			return;
		}
	}