Dialogs Command
 

I'd like to make a built-in dialogs command take an
argument to save a file as a tab-delimited text file.
Here's my code, with "SIMONFile" being the string variable
holding the file name:

Application.Dialogs(xlDialogSaveWorkbook).Show SIMONFile

When I run this, the built-in dialog box defaults to
an .xls file. Is it possible to use a built-in dialog and
change the default to a .txt file? I know how to use the
Workbook.SaveAs command to make this happen, but I'd like
to use the built-in dialog.