Convert month name into number

Another way

Excel Formula

=MONTH(1&A1)

VBA

Sub Sample()
    Dim MonthNm As String
    MonthNm = "September"
    Debug.Print Month(DateValue("01 " & MonthNm & " 2012"))
End Sub

or

Sub Sample()
    Dim MonthNm As String
    MonthNm = "September"
    Debug.Print Application.Evaluate("=MONTH(1&" & Chr(34) & MonthNm & Chr(34) & ")")
End Sub

Replace

Try this...

 =MONTH(DATEVALUE(A1&"1"))

Where A1 cell contains month name.