Date format while export in excel

Hi All,

I am facing an issue while exporting data in to excel. In report I am able to trim timestamp  of a datetime field by using format() and also able to change the format as I like.

But once exporting into  excel, it is opening AS  DD/MM/YYYY  irrespective of data format in the report. My region setting in the desktop is DD/MM/YYYY. So everytime I need to change the  region setting through control panel to  view the data in desired date format. Please help. 

I need to see the  data in DD-MM-YYYY ( separator will be - in place of /) 

Regards,