Excel Interop - Please Help - Thanks

Hi,

Im trying to iterate through worksheets from a work book and basically place each of the cell values into a list box. Here is the code i have so far but i either get null errors or Unable to cast object of type 'System.String' to type 'System.Object[,]'.

using

namespace

{

System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Alias = Microsoft.Office.Interop.Excel;
using System.Collections;EXpublic partial class Form1 : Form

{

{

InitializeComponent();

}

{

Alias.Scansheets(workbook);

public Form1()private void simpleButton1_Click(object sender, EventArgs e)Application app = new Alias.Application();Workbook workbook = app.Workbooks.Open("C:\\Book2.xls", Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

private void Scansheets(Workbook wookBookIn)
int numsheets = wookBookIn.Sheets.Count;
for (int sheetNum = 1; sheetNum < (numsheets); sheetNum++)
Worksheet sheet = (Worksheet)wookBookIn.Sheets[sheetNum];
Range excelRange = sheet.UsedRange;
object[,] valArray = (object[,])excelRange.get_Value(XlRangeValueDataType.xlRangeValueDefault);
foreach (object value in valArray)
if (value != null)
else
{listBox1.items.add(value);

Hope you can  help. it's driving me crazy

Thanks
Anthony