How can I change the import options for an Excel table in InDesign CS5.5?

Hi,

I have a problem with an InDesign script that works this way in ID CS4 and ID CS5, but stops working in ID CS5.5.

What the script should do, is to change the import preferences for a table saved in an Excel file so that I can place an unformatted table into a new textFrame in my InDesign document. The Excel document is an .xlsx-File.

function setExcelImportPrefs() {
    with (app.excelImportPreferences) {
         app.excelImportPreferences.tableFormatting = TableFormattingOptions.excelUnformattedTable;
        }
}

What the script does (or at least seems to do) is: nothing. The table that is placed into the textFrame by the script is always formatted, as this seems to be the standard preference of InDesign CS5.5 for importing tables out of excel files.

Does anybody have a hint for me how to make the script work in ID CS5.5?