Using a Maple-compatible format for the file path with "/" instead of the Windows "\"might be the solution.

My attempt to export to Excel file MapleOutput.xlsx with the following command with Windows-style file path failed:

Export(myarray,"C:\Users\mapleuser\Documents\MapleOutput.xlsx","MyWorksheet", "C7");

Changing the Export command to UNIX-style file path works on my Windows computer:

Export(myarray,"C:/Users/mapleuser/Documents/MapleOutput.xlsx","MyWorksheet", "C7");

Importantly, the command with the UNIX-style file path places the data starting in Excel cell C7 or any other cell the user wants to use. 

My attempt to export array data using the Browse>Export option when looking at the data fails to work as needed.  The exported data always start in cell A1 of the worksheet.  Maple 16 ignores the information about the intended destination cell in the Excel file.

Similarly, attempting to export array data with the simplified command Export(myarray) and then working with the dialog box to provide the additional information about file name, worksheet, and cell destination also fails.  Maple 16 ignores the information about the intended destination cell in the Excel file.

Summary:  Provide file name, worksheet,and destination cell in the Export command of ExcelTools in your Maple file.  In the Export command, use the UNIX-style path for the file name with "/" and not the Windows style path with "\".