Dim cn as ADODB.Connection
Set cn = New ADODB.Connection
.Provider = "Microsoft.Jet.OLEDB.4.0"
.ConnectionString = "Data Source=C:\MyFolder\MyWorkbook.xls;" & _
"Extended Properties=Excel 8.0;"
don't forget to replace "C:\MyFolder\MyWorkbook.xls" with the path and filename of your project
Is there a specific reason you are using excel as a database? It is not a very scalable method. If your users really need to access the data as an excel spreadsheet you can always give them the option to export smaller sets of data through excel.
I say this having developed applications in access, only to port them to SQL Server later on because access kept crashing with lots of data. Excel is similar, when your application is several years old with lots of data things start breaking.
Think about the whole life cycle of your application. Just some food for thought.