Preet,
Printing the Excel sheet is just an ActiveX method call to print the worksheet. To add data to the worksheet, you already have the reference, just call a print method. As for handling large amounts of data, that is a vague question. The data will print how ever you placed it on the worksheet. If what you mean is that you don't want to print out 25 pages every time, the print method has options to only print specific pages or ranges. You may want to play around with a sample spreadsheet to learn the printing options. For help on the ActiveX functions, make sure you have the Visual Basic help installed for Excel.
Randy Hoskin
Applications Engineer
National Instruments
http://www.ni.com/ask