In Visual Basic for Applications (VBA), worksheets are deleted with the Delete method. In AppleScript, delete in the Standard Suite works the same way, except that it allows you to delete lists of several items all at once and avoid repeat loops completely in applications where this behavior is implemented. Note, however, that workbooks must contain at least one worksheet, so you can't delete the last worksheet in a workbook. To delete all but the first sheet in VBA:

On Error GoTo Err_Handler
	Application.DisplayAlerts = False
	For i = Worksheets.Count To 2 Step -1
		Worksheets(i).Delete
	Next i
	Err_Handler:
Application.DisplayAlerts = True

This backwards motion through repeat loops is always required in AppleScript in any case. So the way to do an exact replica is:

tell application "Microsoft Excel"
	set display alerts to false
	try
		set allSheets to (every worksheet in active workbook)
		repeat with i from (count allSheets) to 2 by -1
			delete (item i of allSheets)
		end repeat
	on error
		set display alerts to true
	end try
end tell

But why bother? You're in AppleScript now, so do it the AppleScript way:

tell application "Microsoft Excel"
	set display alerts to false
	try
		delete items 2 thru -1 of (get every worksheet ¬
			of active workbook)
	end try
	set display alerts to true
end tell

Much easier. (But note the explicit get needed.) The try statement is used because if there is in fact just one worksheet to begin with, there will be no item 2 and the statement will error. That is precisely the point you want to be at (just one worksheet) so that you move on and turn error messages (display alerts) back on.

In fact, Microsoft Excel lets you do this without erroring:

tell application "Microsoft Excel"
	set display alerts to false
	try
		delete (every worksheet of active workbook)
	end try
	set display alerts to true
end tell

Without even telling Excel to do so, it leaves the first worksheet in place without erroring or trying to delete it. That's a handy shortcut, but don't count on it in all circumstances.

Deleting a whole list of items, like opening a whole list of items, is a great and powerful advantage of AppleScript, especially in production work.

In all cases, set the application property display alerts to false to get around the Excel safety feature of a separate Alert dialog box for each worksheet about to be deleted. Then turn alerts back on when done.