Extra check so existing spreadsheets don't get overwritten by accident - disable the "update" checkbox in GetArgs dialog, check for xls file existence in xlsarg callback, if True then enable the update checkbox and set it to True so the user has to explicitly uncheck it to overwrite the xls file.  This looks better than simply setting the update checkbox to True by default which might be confusing if the user isn't expecting the xls file to already exist.
Extra check so existing spreadsheets don't get overwritten by accident - disable the "update" checkbox in GetArgs dialog, check for xls file existence in xlsarg callback, if True then enable the update checkbox and set it to True so the user has to explicitly uncheck it to overwrite the xls file.  This looks better than simply setting the update checkbox to True by default which might be confusing if the user isn't expecting the xls file to already exist.
tectronics/metageta