Excel.Range.Find method

I am using Excel interop object and trying to find a date in a specified range by below method

Excel.Range rngFind = WS.get_Range(strFromRange, strToRange).Find(strFind, Type.Missing,
                Excel.XlFindLookIn.xlFormulas, Excel.XlLookAt.xlPart, Excel.XlSearchOrder.xlByRows,
                Excel.XlSearchDirection.xlNext, false, false, false);

but i get rngFind as null always my strFind = "Sep-08" i tried with both Excel.XlFindLookIn.xlFormulas and Excel.XlFindLookIn.xlValues

my excel file looks like this

Sep-08  Oct-08  Nov-08  Dec-08  Jan-09  Feb-09  Mar-09  Apr-09  May-09  Jun-09  Jul-09

where as wheni click on Sep-08 cell i get 9/1/2008 in the formula field in Excel i have also tried searching for 9/1/2008 but it varies system by system as per the RegionalSettings Date format...

Please help me. basically i am doing to get the cell address of the finding string

Using Office 2007, Interop generated directly from Visual Studio. I used the following code to find the cell in question:

using System.Reflection;
using Microsoft.Office.Interop.Excel;

object False = false;
object True = true;

_Application excel = new Microsoft.Office.Interop.Excel.ApplicationClass();

Workbook wb = excel.Workbooks._Open(@"C:\tmp\StackOverflow.xlsx",False, False,Missing.Value,Missing.Value,False,False,Missing.Value,Missing.Value,False,Missing.Value,Missing.Value,True);

_Worksheet ws = (_Worksheet)wb.Worksheets[1];

string from = "A1";
string to = "B1";

Range rng = ws.get_Range(from,to);

Range findRng = rng.Find("Sep-08",Missing.Value,XlFindLookIn.xlValues,Missing.Value,Missing.Value,XlSearchDirection.xlNext,False,False,Missing.Value);

You can find the Microsoft example at How to automate Excel by using Visual C# to fill or to obtain data in a range by using arrays.