Open, update and convert 2007--2003 then close without any prompt
 

Hi,
I have some vbscript that opens up an excel 2007 file which then runs ahead
and updates a load of data. What I need it to do is

Open and Run the macro
Save AS .xls file, overwritting the existing file (it will always be the
same file, in the same location)
The problem Im having is it needs to run overnight without intervention so
how can I have it run the save as and overwrite without prompting for
compatibility issues or file already exists?
Basically am after a way of opening and closing the file silently
any ideas greatly appreciated

thanks