Solution
You can implement such a functionality by combining Excel Get Worksheet.vi and Excel Workbook Properties.vi.
The example is shown below.
In this example, after all sheet name is extracted, these names are listed in combo box indicator so that the user can choose Excel sheet from this combo box.
The index which is a result of Decimal String To Number shows the chosen Excel sheet's index number.
Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW block diagram.