i am guessing you are using this from access if so you have to set up
an application object and what not if you havent done so already
'opens workbook
Dim objexcel As New Excel.Application
Set objexcel = CreateObject("Excel.Application")
objexcel.Workbooks.Open "c:/path of workbook/workbook name.xls"
objexcel.Visible = True
'counts sheets
msgbox objexcel.Sheets.Count
if you are in the wrong group and should be in an excel group use
ActiveWorkbook.Sheets.Count
hope this helps
Regards
Kelvan