GregorianCalendar day of the week

Hi Guys

I have an excel sheet with a column date from 2003 (format : 2015/02/10) and column sales. I want to extract( last year,current week, today's day name )sales numbers.  I have tried my code below but I'm getting error "cannot convert string"Wednesday" to double" any idea how to ? thank you

Dim MyCalendar As Calendar = New GregorianCalendar
        Dim culture = New System.Globalization.CultureInfo("EN-US")

        Dim dayname As String = culture.DateTimeFormat.GetDayName(Now.DayOfWeek)

        Dim lastCurrentweek = MyCalendar.GetWeekOfYear(
          Now,
          CalendarWeekRule.FirstFourDayWeek,
          DayOfWeek.Sunday
      )
        Dim lastCurrentyear = MyCalendar.GetYear(Now) - 1

Dim dayrecord = (
                From Row In eventcal.AsEnumerable
               Where MyCalendar.GetWeekOfYear(Row.Field(Of DateTime)("date"),
                                              CalendarWeekRule.FirstFourDayWeek,
                                              DayOfWeek.Sunday) = Currentweek And MyCalendar.GetYear(Row.Field(Of DateTime)("date")) = lastCurrentyear And _
 MyCalendar.GetDayOfWeek(Row.Field(Of DateTime)("date")) = dayname
               Select Row.Field(Of Double)("sales")
               )