Transfer data from mutiple csv to single excel workbook

I have 3 csv files and want to import all data respectively to an excel with data transferred to 3 sheets(sheet1,sheet2,sheet3) in a single workbook using c#.net.Any help is appreciated.
    Excel.Application xl=new Excel.Application;
    Excel.Workbook wb=new Excel.Workbook;
    Excel.Worksheet ws1=new Excel.worksheet;
    Excel.Worksheet ws2=new Excel.worksheet;
    Excel.Worksheet ws3=new Excel.worksheet;
    string csv1=@"c:\SS1.csv";
    string csv2=@"c:\SS2.csv";
    string csv3=@"c:\SS3.csv";
    wb=xl.Workbooks.Open(csv1);

I'm stuck here.How do i access the other 2 csv files.