If you have report generation tool kit you can use it for reading and writing into Excel. If you don't have it, then you can use Activex methods to do it. Check the attached VI. You will get a good understanding of doing it.
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I do have report generation toolkit ... I don't know how to use it because I've never used it...
How should I give the path where I want to save the excel file?
Do you really want the Excel file or you can have a .xls file that you can view using MS Excel?. If you just need a file you have to view using excel then its very simple.
Then you can do like this. I guess this should be sufficient