ASP.NET Calendar IsSelectable false

hi, im having a problem on my asp calendar.

It is currently reading in data from a database.

I want it to be able to disallow somone from clicking on a date which has text in it.

here is my code.

      protected void eventscalendar_DayRender(Object Src, DayRenderEventArgs E)
      {
            StringBuilder strEvents = new StringBuilder();
            strEvents.Append("<span style=\"font-size:80%\">");
            
            foreach (DataRow row in ds.Tables["events"].Rows)
            {
                  DateTime eventdate = (DateTime)row["eventdate"];
                  if (eventdate.Equals(E.Day.Date))
                        strEvents.Append("<br />" + row["eventtext"]);            
            }
            strEvents.Append("</span>");
            E.Cell.Controls.Add(new LiteralControl(strEvents.ToString()));
            }

i have tried this

      if (E.Cell.Controls.Count == 1)
      {
      E.Day.IsSelectable=false;
      }

and

E.Day.IsSelectable=false;

but it either disables all the dates or doesnt.

can anyone help me?

thanks