Are you using the commands from version 6 in version 8?
In version 7 & 8 they added some new commands and naming the table and using overwrite/ append is new.
Look on the help under Chapter 9.
In your case I think you you to change
/exp: "W:...345.xls" /t"
/exp: "W:...345.xls" /expfileopt:[option]
were option is either "overwrite", "add", or "skip". If you have version 8 PRO, you can also use /exptable:[Tablename], were table name is the name of the sheet in Excel, or the table name if you used access. These commands can be in any order in the command line, and should have quotes around ant file names with spaces.
Let us know how you make out.
Edited for clarity
[size="1"][ September 28, 2005, 09:35 PM: Message edited by: Bruce Reed ][/size]