Retrieve last day of the month but hitting error

If you month "July" in "B1" is a string then ,Perhaps

Sub MG04Sep49
Dim MyMonth As String
Dim Year As String
Dim EndDate As Date
Dim Mth As Integer
    MyMonth = Range("B1").Value 'July '
        Year = Range("D1").Value '2014
            Mth = Month("01-" & MyMonth & "-" & Year)
                EndDate = DateAdd("d", -1, DateSerial(Year, Mth, "1"))
End Sub

Regards Mick