Converting Excel w/a droplet

I’d like to have a droplet that will convert an Excel '98 document to an Excel 4.0 document. Can someone point me in the right direction? I don’t know how to tell Excel to make the conversion. Thanks.

Here’s what I’ve got so far:

on open
	tell application "Microsoft Excel"
		Save ActiveWorkbook As xlExcel4Workbook Password "" WriteReservedPassword ""
	end tell
end open