Replace these statements in your code

from

// Create an instance of Excel.
oExcel = new Excel.Application();

// Add a workbook.
oBook = oExcel.Workbooks.Add(oMissing);


to
oExcel = new Excel.Application();

oBook = oExcel.Workbooks.open("C:\temp\book1.xls);


I assume you are creating an Excel Application and then opening a workbook.
If you are just adding code to the opened workbook then use this

oBook = Thisworkbook


If you are working in a macro and not C# you need to put a "SET" in front of
each command.

"Aerojade" wrote:

I have found references and code on the net which helps me add code in the
form of an Excel Macro. However it shows how to create a new module and then
add functions to it. How to add functions to the thisWorkbook part of the
File.

the link that shows how to programatically add macro o a new module is:
http://support.microsoft.com/kb/303872

i dont want to add it to a new module but to "ThisWorkbook"

Please help