This is a thrid party tool that was created a while ago. I had to dig around to find the tool and how to get it working below are some forum posts that I found on this and what I had to do to get it working in QC / ALM 11.52.

http://screencast.com/t/5NsE6IkTPX
http://screencast.com/t/nuKfOwDLR
http://screencast.com/t/iI6C17vq

So what you will need to do is:

1. Open the Excel spreadsheet and save the file as file type Excel Maro Enabled Workbook (XLMS)
2. You will need to download the following file: http://windowsxp.mvps.org/comdlg32.htm
3. Copy it to the %systemroot%system32 directory
4. Open a comand prompt and enter the following without quotes ''regsvr32 %Systemroot%System32comdlg32.ocx''
5. Open the spreadsheet and click the button that the top of the page to enable the macros and the login window will appear

You may have to restart your workstation if you are having trouble after the above steps

Here is the forum thread again where the creator actually gets involved in the troubleshooting.

http://h30499.www3.hp.com/t5/Quality-Center-Support-and-News/Export-test-cases-form-quality-center-to-excel-sheet-or-XML/td-p/5711561#.U-z0nfldU3c