If (e.Row.RowState = DataControlRowState.Edit) OrElse (e.Row.RowState = (DataControlRowState.Edit Or DataControlRowState.Alternate)) Then
Dim id as Integer = DirectCast(e.Row.FindControl("yourLiteral").Text
Dim ddl As DropDownList = DirectCast(e.Row.FindControl("YourDDL"), DropDownList)
'Here, add or bind your dropdownlistvalues
ddl.Items.FindByValue(id).Selected = True