The following example activates Sheet1 in the workbook named Cogs.xls (the workbook must already be open in Microsoft Excel). You cannot set the name by using this property if you need to change the name, use the SaveAs method to save the workbook under a different name.
The Name property returns the workbook name. All workbooks are included in the index count, even if they are hidden. Activating a workbook doesn't change its index number.
Workbooks(1) is the first workbook created, and Workbooks(Workbooks.Count) is the last one created. The index number denotes the order in which the workbooks were opened or created. The following example activates workbook one. Use Workbooks ( index), where index is the workbook name or index number, to return a single Workbook object. If you are creating an add-in from your Visual Basic code, you should use the ThisWorkbook property to qualify any statement that must be run on the workbook that you compile into the add-in. In this case, the active workbook is the workbook calling the add-in, whereas the ThisWorkbook property returns the add-in workbook.
However, if the Visual Basic code is part of an add-in, the ThisWorkbook property won't return the active workbook. In most cases, this is the same as the active workbook. The ThisWorkbook property of the Application object returns the workbook where the Visual Basic code is running. The Workbooks collection contains all the Workbook objects currently open in Microsoft Excel. The Workbook object is a member of the Workbooks collection.