Hi,
Thank you for your interest in Syncfusion products.
You can use row and column numbers to refer a range. Here is the code snippet:
sheet[1, i].Text = "Col " + i.ToString();
I have placed the sample here.
http://help.syncfusion.com/samples/XlsIO.Windows/F95290/F95290.zipPlease let us know if you have any questions.
Regards,
Geetha