hi all.. do anyone know how to add a new column in gridview using vb.net syntax?

the column that i want to add is not bind to any database unlike the other column in the same gridview.


i try to use
GridView1.Columns.Add("Percentage")
but it turn out to be error.
the error said " Value of type 'String' cannot be converted to 'System.Web.UI.WebControls.DataControlField'"



i'm still new in vb.net and hope that all of you can help me

thanks in advance