If Excel is installed on the current computer, Summaries can be exported to a new Worksheet using the
Export to Excel option.

The first time this function is executed, the function will prompt the user to locate the Excel.exe file.

A dialog box with display and the user must navigate to the Excel installation folder and find
the required file.  Once this file is located, its full path is stored by Tract Manager in the registry
and this portion of the function should not be executed again.

After the Excel file is located, clicking the Export to Excel button will create a new workbook
containing the selected Land Use Summary.