Help with Security - please!

Question

I have an applet whose codebase is http://www.our_site.com:7777/web_reports/graph/sExcelWriterApplet.jar that needs to do two things normally prohibited in Java:
Run Excel (located at C:\Program Files\Microsoft Office\Office10\excel.exe)
Store and read a temporary file in java.io.tmpdir
So far the only way I have been able to accomplish this is by having the following wide-open .java.policy file:
grant {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "<<ALL FILES>>", "execute";
This works but is obviously unsafe for distribution.
Here are some things I have tried that SHOULD work but do not:
grant codeBase "http://www.our_site.com:7777/web_reports/graph/" {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "<<ALL FILES>>", "execute";
grant codeBase "http://www.our_site.com:7777/web_reports/graph/sExcelWriterApplet.jar" {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "<<ALL FILES>>", "execute";
Thinking that maybe it didn�t like the port specification, I tried the following two:
grant codeBase "http://www.our_site.com/web_reports/graph/sExcelWriterApplet.jar" {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "<<ALL FILES>>", "execute";
grant codeBase "http://www.our_site.com/web_reports/graph/" {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "<<ALL FILES>>", "execute";
Trying to restrict the file it�s executing rather than the codepath:
grant {
permission java.util.PropertyPermission "java.io.tmpdir", "read";
permission java.io.FilePermission "${java.io.tmpdir}${/}HOTSalesQuery.xls", "read, write, delete";
permission java.io.FilePermission "C:\\Program Files\\Microsoft Office\\Office10\\EXCEL.EXE", "execute";
NONE of the above work. I�d be extremely grateful for any suggestions. This is a very high profile project and I need to get this working ASAP. I am using Java 2, version 1.4.2_06, if that helps.
Strangely, the error that gets reported is the reference to the Java.io.tmpdir, though that doesn't change between the working and nonworking versions.
Thanks in advance for any suggestions.

Answer 1

The applet is signed, and though I did not include examples, I tried that too with no success. As rather a Java novice, though, it's possible I did it incorrectly; but the applet DOES pop up the familiar "Do you trust content from blabla" window, so I think I at least signed it correctly.
Thanks for your response.