Excel file format is not only a matter of extension: an excel workbook (.xls) contains several informations about creator name and date, styles used, various sheets contained in the workbook, formulas and macros embedded in the sheets and so on: this is not a simple format to generate, but in your case you may not need all this stuff since you simply want to load a file and separate data in columns.
From what you say, it seems that data is separated with spaces: if you can modify the program that generates test data, you can separate various items in a row by means of tabs (embedding "\t" in the format string in FmtFile) and name the file with .CSV extension: this way excel should automatically open the file and distribute its contents in columns as you want.
