Changing the sequence of export report format

SonalD

When the export report dialog box opens , the export report format dropdown options are like ppt, doc,pdf,postscript,xls.
For user convenience and frequency of usage , I need to configure it to the sequence xls,pdf,doc,postscript ,ppt .
If any one could tell where is this dialog designed and where is the sequence specified, it would be very helpful.

Thanks,
Sonal