In the Visual Studio.NET Evironment, right-click on a toolbox tab and select add/remove items. There should be an Excel Spreadsheet 9.0, 10.0, or 11.0 control depending on your version of Office. I believe it is located in the .NET Frameworks tab. If not, it would be under the COM Components tab. Select the control and click OK. The control will then be added to your toolbox.
I cannot find the object. Is it the MicroSoft Spreadsheet 10.0? If so, I have it loaded, but I cannot add an existing workbook to it. How can this be done, or better, how can I get the Excel object?