All of these functions are documented by Microsoft. If you install the Visual Basic Help with Microsoft Office installation, then the CVI function panels will launch this help for you. Item functions are an extremely common function in ActiveX programming for retrieving a specific item in a collection. Sheets is the collection and a Worksheet is the item. To retrieve a different item you just ask for a different index. Change the index parameter to CA_VariantInt(2) instead of CA_VariantInt(1).
Best Regards,
Chris Matthews
Measurement Studio Support Manager