Error when opening an Excel file: "The file you are trying to open, '.xls.xls', is in a different format than specified by the file extension. Verify that the file is not corrupted and is from a trusted source before opening the file..."

I found a way to fix the error we're receiving when we open the XLS file output--I haven't implemented it yet and I'm hoping you can steer me in the right direction: the cells need binary packing for M$ output.

For example, take the following proof-of-concept code (shove it all in a PHP file and access the file in your browser):

//Beginning of file...
function xlsBOF() {
   echo pack("ssssss", 0x809, 0x8, 0x0, 0x10, 0x0, 0x0);  
   return;
}

//End of file...
function xlsEOF() {
   echo pack("ss", 0x0A, 0x00);
   return;
}

//Creates a heading...
function xlsWriteLabel($Row, $Col, $Value ) {
   $L = strlen($Value);
   echo pack("ssssss", 0x204, 8 + $L, $Row, $Col, 0x0, $L);
   echo $Value;
   return;
}

//Test Data
$result='this is a test';

//Send Headers
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Type: application/force-download");
header("Content-Type: application/octet-stream");
header("Content-Type: application/download");;
header("Content-Disposition: attachment;filename=test.xls ");
header("Content-Transfer-Encoding: binary ");

//XLS Data Cell
$title = 'test';
xlsBOF();
xlsWriteLabel(1,1,$result);
xlsEOF();

That code above creates an XLS file without that irritating corruption message at the beginning but the problem is that the module appears to be using Drupal theming to theme the Excel output--which isn't going to fly as far as Excel is concerned.

The file I'm assuming this code should be applied to is "views_data_export.theme.inc". Is this correct? If so, where at should the change occur? For headings, I was thinking that it would be in "template_preprocess_views_data_export_msoffice_header()" and for the body, "template_preprocess_views_data_export_msoffice_body()". Is this right?

Any insight is appreciated.