web page opens excel then saves as.csv

I have an internal web site that needs to do the following.  open an excel file and then save each worksheet as a .csv file.   

on the web page i have a fileupload control that allows the user to find the excel file they wish to convert and a button that when clicked will run the code i need help creating.  I try to add the reference for Microsoft excel 11.0 but it does not add the dll to the bin automatically.  Is there a better way to do this?  can you help me do it this way?  please help, and thank you in advance.  My code behind follows
protected void btnCreate_Click(object sender, EventArgs e)
{
Workbook workbook = new Workbook();
workbook.Open(FileUpload1.PostedFile.FileName);

for (int i = 0; i < workbook.Worksheets.Count; i++)
...