Java Database Connectivity (JDBC)

Hi all experts,
I am developing a program which uses the JDBC to insert records into MS *.xls files. It worked fine for reading. But when inserting: it shows the exception:

java.sql.SQLException: [Microsoft][ODBC Excel Driver] Operation must use an updateable query.

I was so confused, because I already used PreparedStatement.executeUpdate() method, the following is my code:
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String insertStmnt = "INSERT INTO [test1$] values(' ', " + "'" + result +"','')";

PreparedStatement testStmnt = testConn.prepareStatement(insertStmnt);
testStmnt.executeUpdate();
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Any one has some suggestion?
I am so worried! Coz the project is due soon!

Thanks a lot!

Michael